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I. II ..II’ I .u . 1 1. 1”. . .I. . 1 . 1. I . {I}... I I ..1.I1.III1 t .1 ...I.. .. 1.1!, 1 . I.I.I I 1.1 1 . I ...... II. .II. 1I1I IIIDI II' v 11.1I. . II . 1 .I I I ..1 I 1 O. I A I . I .. .11I I . .I. I3, ..PA I . ..1 . . .1 . . I I . In 1 . O. .. . .. . . . 1 1 1 I. . 1 I . . 1 1 .0. 18.1! . . I.‘ .- 1. .. ... . u. .. 1 1 . . . . . I . 0 . . . 1. . . I "g" Llnnanv 3M? MICIllgeis; state V , University a) If, u\ This is to certify that the dissertation entitled EXPLORATORY SYNTHESIS OF COMPLEX INTERMETALLIC GERMANIDES AND INDIDES USING MOLTEN INDIUM AS A FLUX presented by MARIA CHONDROUDI has been accepted towards fulfillment of the requirements for the PhD degree in Chemistry [47 axe/me Major Professor’s Signature é/Zé/a? Date MSU is an Affirmative Action/Equal Opportunity Employer PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 5/08 K:IProlecc&Pres/CIRC/DaIeDue indd EXPLORATORY SYNTHESIS OF COMPLEX INTERMETALLIC GERMANIDES AND INDIDES USING MOLTEN INDIUM AS A FLUX VOLUME I By Maria Chondroudi A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chemistry 2009 ABSTRACT EXPLORATORY SYNTHESIS OF COMPLEX INTERMETALLIC GERMANIDES AND INDIDES USING MOLTEN INDIUM AS A FLUX By Maria Chondroudi Molten metal fluxes can be excellent alternative to the conventional synthetic methods for the exploratory synthesis of new intermetallic compounds. Our group has initiated a project where molten Al and Ga are used to investigate the reactivity of the quaternary systems RE/TM/Al/Si or Ge and RE/TM/Ga/Si or Ge which has resulted in a numerous new ternary and quaternary phases. We have recently expanded this work to also include molten In as a synthetic medium in parallel to Al and Ga systems. The main goal of this dissertation was to exploit the ability of liquid In as a reactive flux in the system REfTM/Ge/In and discover new complex multinary compounds that could exhibit interesting structural features as well as chemical and physical properties. Particularly we have performed explorations in the system RE/Co(Ni)/Ge/In and we have succeeded in isolating two new quaternary compounds: the RE7Co4InGe12 and Yb7Ni41nGe12. Their 3D-network features three different types of channels, propagating along the c-axis, in which the Yb atoms are situated. The Yb analogs exhibit mixed- valence behavior and the Yb3I/Yb2+ ratio is slightly temperature dependent. Interestingly, the reaction targeting the Dy7Co4InGe12 member also produced the Dy4CoInGe4 phase which crystallizes as a new structure-type. The Dy4CoInGe4 structure is related to the RE7TM41nGe12 structure and possesses lZ-membered and S-membered channels propagating along the b-axis in which the Dy atoms are found and CozGe(1)2 ribbons. Dy4CoInGe4 exhibits ferromagnetic ordering at ~ 40 K and a complex magnetic behavior below this temperature. By studying the system RE/Au/Ge/In we obtained three new quaternary compounds Yb3AuGezln3, CeAuGeIn and EuAuGeInz. Yb3AuGezln3 crystallizes as an ordered variant of the YbAuIn structure. Both Yb compounds, which were studied in parallel, are intermediate- or mixed-valence compounds and display intriguing magnetic properties which are strongly dependent on the form of the measured sample and other experimental conditions and vary from being paramagnetic to exhibit ferromagnetic ordering. The ordered orthorhombic CeAuGeIn and the disordered tetragonal EuAuGeInz compounds have closely related layered structures. Both compounds seem to undergo antiferromagnetic and ferromagnetic transitions below 12 K whereas EuAuGeInz shows possible additional magnetic structures as seen in the low field magnetic measurements. Synthetic investigations of the systems Yb/TM/Ge in liquid In resulted in the particularly interesting Yb4TMGCg (TM = Fe, Cr, Co) compounds for which (3+1)D crystallography revealed the existence of superstructures due to modulated Ge nets and partial TM occupancies. All three compounds exhibit Yb mixed—valence behavior with the valence constantly changing with the temperature and anomalous thermal expansion behavior below ~ 100 K. Additionally, heat capacity measurements for the Cr analog suggest possible heavy-fermion behavior whereas resistivity measurements for the Fe analog show unusual temperature dependence. Finally, explorations in the ternary systems RE/Cu(Ag)/In led to the formation of the RECu6+xIn6 and YbAg5131n633 compounds which the crystallize as an orthorhombic variant of the Tth12 structure-type. The Yb analogs exhibit mixed-valence behavior. Copyright by MARIA CHONDROUDI 2009 ACKNOWLEDGMENTS First and foremost I would like to express my deep and sincere gratitude to my advisor, Professor Mercouri G. Kanatzidis, for giving me guidance and encouragement both as mentor and a friend during my PhD years. I am grateful to him for the opportunity to work at Argonne National Laboratory (ANL) for the last two years where I had the opportunity to grow and mature as a scientist and to access facilities not otherwise available at Michigan State University. I would also like to thank my committee members, Professors Smith, Weliky, Mahanti and Duxbury for their valuable suggestions and discussions. My collaborators and mentors both at MSU and at the Materials Science Division at ANL Dr Lolee, Dr Mitchell, Dr Gray, Dr Clauss, Dr Q’Li, Dr Welp, Dr Schlueter, Dr Kwok, Dr Osborne and many others. I owe special thanks to Dr Balasubramanian at the Advanced Photon Source at ANL for being an exceptional collaborator, mentor and friend and for being willing to work endless hours day and night with me at the beamline. It would have not been possible for me to succeed without the unconditional love and support of my parents who have dedicated their lives into giving the highest education and opportunities to their kids. The love, faith and advice from my brothers Stelios and Kostas and my dearest friend D. Rivera helped me through the tough and Finally, I would like to thank all the Kanatzidis group members for their help and friendship particularly, Dr Malliakas for breaking down all the crystallographic mysteries, Dr Salvador and Dr Todorov. TABLE OF CONTENTS LIST OF TABLES .................................................................................... x LIST OF FIGURES ............................................................................... xvii Chapter 1. Introduction ............................................................................ l 1.1 Introduction to Intermetallics, Selected Properties and Applications ......... 1 1.2 Motivation for the Use of Molten Metal Fluxes as Synthetic Media .......... 4 1.3 Use of Molten Al, Ga and In for the Exploratory Synthesis of Rare Earth Transition Metal and Tetrel Containing Intermetallic Compounds ............ 6 References ........................................................................... 12 Chapter 2. Mixed Valency in Yb7TM41nGe|2 (TM = Co, Ni): a Novel Intermetallic Compound Stabilized in Liquid Indium ......................................... 21 2.1 Introduction .......................................................................... 21 2.2 Experimental Section ............................................................... 22 Reagents ........................................................................ 22 Synthesis ........................................................................ 23 Elemental Analysis ............................................................ 24 X-ray Crystallography ........................................................ 25 Differential Thermal Analysis ............................................... 32 Magnetic Measurements ...................................................... 32 X-Ray Photoemission Spectroscopy ........................................ 32 X-ray Absorption Near Edge Spectroscopy (XANES) ................... 33 Magneto-Transport Measurements .......................................... 34 2.3 Results and Discussion ............................................................ 34 Reaction Chemistry ............................................................ 34 Structure ........................................................................ 36 Magnetic Measurements ...................................................... 45 XPS Measurements ............................................................ 49 XANES Measurements ....................................................... 50 Magneto-Transport Measurements .......................................... 54 2.4 Conclusions .......................................................................... 55 References ........................................................................... 57 Chapter 3. Flux Synthesis of the New Quaternary Intermetallic Dy4CoInGe4 Exhibiting Complex Magnetic Behavior ...................................................... 61 3.1 Introduction .......................................................................... 61 3.2 Experimental Section ............................................................... 63 Reagents ........................................................................ 63 vi 3.3 3.4 Chapter 4. 4.1 4.2 4.3 4.4 Chapter 5. 5-I-l. 5—1-2. Synthesis ........................................................................ 63 Elemental Analysis ............................................................ 64 X-ray Crystallography ......................................................... 65 Magnetic Measurements ...................................................... 68 Results and Discussion ............................................................ 69 Reaction Chemistry ............................................................ 69 Structure ........................................................................ 70 Magnetic Measurements ...................................................... 83 Conclusions .......................................................................... 90 References ........................................................................... 91 Flux Synthesis of Yb3AuGe21n3: an Ordered Variant of the YbAuIn Structure Exhibiting Mixed-Valent Yb Behavior .............................. 95 Introduction .......................................................................... 95 Experimental Section ............................................................... 97 Reagents .......................................................... . ............. 97 Synthesis ........................................................................ 97 Elemental Analysis ............................................................ 98 X-ray Crystallography ......................................................... 99 Magnetic Measurements ........................................... , ......... 102 X-ray Absorption Near Edge Spectroscopy (XANES) .................. 103 Resistivity ..................................................................... 1 04 Heat Capacity ................................................................. 104 Thermoelectric Power ....................................................... 105 Results and Discussion ........................................................... 105 Reaction Chemistry .......................................................... 105 Structure ....................................................................... 106 Magnetic Measurements .................................................... 114 Magnetic Measurements Under Variation of Experimental Parameters .................................................................... 120 XANES Measurements at Ambient Pressure ............................. 151 Magnetotransport Measurements .......................................... 153 Heat Capacity Measurements ............................................... 156 Conclusions ........................................................................ l 59 References .......................................................................... 161 CeAuGeIn and EuAuGeInzz New Quaternary Interrnetallics Grown from PART 1. Synthesis and Characterization of CeAuGeIn: Exhibiting Complicated Magnetic Structure ................................................ 168 Introduction ......................... v ............................................... 168 Experimental Section ............................................................. 170 Reagents ....................................................................... 170 Synthesis ...................................................................... 171 Elemental Analysis .......................................................... I72 X-ray Crystallography ....................................................... 173 vii S-II-l. 5-II-2. 5-II-3. 5-II-4. Chapter 6. 6.1 6.2 6.3 Magnetic Measurements .................................................... 176 Resistivity ..................................................................... 177 X-ray Absorption Near Edge Spectroscopy (XANES) .................. 177 Results and Discussion ........................................................... 178 Reaction Chemistry .......................................................... 178 Structure ....................................................................... 179 Magnetic Measurements .................................................... 185 Magnetotransport measurements .......................................... 192 XANES Measurements ...................................................... 193 Conclusions ........................................................................ 195 PART 11. Synthesis and Characterization of EuAuGeInz .................... 197 Introduction ......................................................................... 197 Experimental Section ............................................................... 198 Reagents ....................................................................... 170 Synthesis ...................................................................... 198 Elemental Analysis .......................................................... 199 X-ray Crystallography ....................................................... 200 Magnetic Measurements .................................................... 204 Results and Discussron204 Reaction Chemistry .......................................................... 204 Structure ....................................................................... 205 Magnetic Measurements .................................................... 213 Conclu51ons215 References .......................................................................... 21 7 Yb4TMGeg (TM = Fe, Cr and Co) an In Flux Grown Intermetallic: Exhibiting Temperature Induced Yb Valence Fluctuation and Anomalous Thermal Expansion below ~ 100 K .............................. 224 Introduction ........................................................................ 224 Experimental Section ............................................................. 227 Reagents ....................................................................... 227 Synthesis ...................................................................... 227 Elemental Analysis .......................................................... 228 X-ray Crystallography ....................................................... 229 Magnetic Measurements .................................................... 248 X-ray absorption Near Edge Spectroscopy (XANES) ................... 249 Heat Capacity ................................................................. 249 Resistivity ..................................................................... 250 Results and Discussion ........................................................... 250 Reaction Chemistry .......................................................... 250 Structure ....................................................................... 252 Magnetic Measurements .................................................... 262 XANES Measurements at Ambient Pressure ............................. 268 Temperature Dependent Single Crystal X- -Ray Diffraction Measurements ................................................................ 275 Heat Capacity Measurements for Yb4CrGe3 .............................. 285 viii 6.4 Chapter 7. 7.1 7.2 7.3 7.4 Chapter 8. Electrical resistivity measurements for Yb4FeGeg ....................... 287 Conclusions ........................................................................ 288 References .......................................................................... 29 l Exploratory Studies on the Ternary Systems RE/Cu/In and Yb/Ag/In Employing In as Flux ............................................................ 297 Introduction ........................................................................ 297 Experimental Section .............................................................. 299 Reagents ....................................................................... 299 Synthesis ...................................................................... 299 Elemental Analysis .......................................................... 300 Single Crystlal X-ray Diffraction .......................................... 301 High Resolution Powder X-ray Diffraction .............................. 302 Magnetic Measurements .................................................... 322 X-ray absorption Near Edge Spectroscopy (XANES) ................... 322 Results and Discussion ........................................................... 323 Reaction Chemistry .......................................................... 323 Structure ....................................................................... 325 Magnetic Measurements .................................................... 331 XANES Measurements ...................................................... 349 Conclusions ........................................................................ 353 References ..................................................................... 355 Conclusions and Future Work .................................................... 360 ix Table 2-1. Table 2-2. Table 2-3. Table 2-4. Table 2-5. Table 2-6. Table 2-7. Table 2-8. Table 3-1. Table 3-2. Table 3-3. Table 3-4. Table 4-1. Table 4-2. LIST OF TABLES Crystal data and structure refinement data for RE7Co4InGelz (RE = Dy, Ho, Yb) ........................................................................... 27 Atomic coordinates (x 104) and equivalent isotropic displacement para- 3 meters (A2 x 10 ) for RE7Co4InGe12 (RE = Dy, Ho, Yb)..................28 Anisotropic displacement parameters (A2 x 103) for RE7C04InGe12 (RE = Dy, Ho, Yb). The anisotropic displacement factor exponent takes the 2 2 2 II 12 form: -27r [h a* U + ...+2hka*b*U ] ...................................... 29 Crystal data and structure refinement data for Yb7Ni4InGe12 .................................................................... 30 Atomic coordinates (x 104) and equivalent isotropic displacement para- meters (A2 x 103) for Yb7Ni4InGe12.............................................3l Anisotropic displacement parameters (A2 x 103) for Yb7Ni4InGe12 (RE = Dy, Ho, Yb). The anisotropic displacement factor exponent takes the form: -21r2[h2a"‘2UI l+ +2hka*b*U12] ..................................... 31 (Bond lengths [A] for RE7Co4InGe12 (RE = Dy, Ho, Yb) .................. 43 Bond lengths [A] for RE7Ni4InGe12.................................................44 Crystal data and structure refinement data for Dy4CoInGe4 .............. 66 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for Dy4CoInGe4........ ...................... ‘ ......................... 67 Anisotropic displacement parameters (A2 x 103) for Dy4CoInGe4 ......................................................................................... 68 Selected Bond lengths [A] for Dy4CoInGe4.....................................82 Crystal data and structure refinement data for Yb3AuGezIn3 and Yb3Au3In3.............. .......................................................................... 1‘00 Atomic coordinates (x 104) and equivalent isotropic displacement para- Table 4-3. Table 4-4. Table 4-5. Table 4-6. Table 5-1-1. Table 5-I-2. Table 5-1-3. Table 5-I-4. Table 5-II-1. Table 5-lI-2. Table 5-II-3. Table 5-II-4. Table 5-II-5. Table 5-II-6. 2 3 meters (A x 10 ) for Yb3AuGezln3 and Yb3AU3In3 .............................. 101 Anisotropic displacement parameters (A2 x 103) for Yb3AuGe21n3 and Yb3Au3In3. The anisotropic displacement factor exponent takes the 2 2 2 11 12 form: -21r [h a* U + +2hka*b*U ] .................................... 101 Selected Bond lengths [A] for Yb3AuGezln3 and Yb3Au3In3 .................................................................................... I I4 Summary of the magnetic behavior for various samples of Yb3AUGCzIn3 ................................................................... I 50 Summary of the magnetic behavior for various samples of YbAuIn.. ...................................................................................... 150 Crystal data and structure refinement data for CeAuGeIn ...................................................................... 174 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for CeAuGeIn .......................................................... 175 Anisotropic displacement parameters (A2 x 103) for CeAuGeIn The anisotropic displacement factor exponent takes the form: - 2 2 2 11 12 21: [h a* U +...+2hka*b*U ]...... .................................................. 175 Selected bond lengths [A] for CeAuGeIn ............................................ 185 Crystal data and structure refinement data for EuAuGeInz in 14mm and I4/mmm space groups ...................................................................... 201 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for EuAuGeInz in 14mm space group...................202 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for EuAuGeInz in I4/mmm space group ...............202 Anisotropic displacement parameters (A2 x 103) for EuAuGeInz in 14mm space group .............................................................. 203 Anisotropic displacement parameters (A2x103) for EuAuGeInz in 14/mmm space group ........................................................... 203 Selected bond lengths [A] for EuAuGeInz ........................................... 211 xi Table 6-1. Table 6-2. Table 6-3. Table 6-4. Table 6-5. Table 6-6. Table 6-7. Table 6-8(I). Table 6-8(II). Table 6-9. Table 6-10. Table 6-11. Table 6-12. Initial crystal data and structure refinement data for Yb4CI‘GCg ........ 232 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for Yb4CrGe3 ......................................................... 233 Anisotropic displacement parameters (A2 x 103) for Yb4CI'GCg ..................................................................................... 233 Crystal data and structure refinement data for Yb4CrGeg at 100.0(3) K ................................................................................. 234 Atomic coordinates (x104), Fourier components of the displacive modulation (x104) and equivalent isotropic displacement parameters (A2x104) for Yb4CrGeg at 100.0(3) K with estimated standard deviations in parentheses .................................................................. 235 Fourier components of the atomic thermal parameters modulation (x103) for Yb4CrGe3 at 100.0(3) K with estimated standard deviations in parentheses ..................................................................... 236 Fourier components of the occupational modulation for Yb4CrGeg at 100.0(3) K with estimated standard deviations in parentheses ......... 236 Bond lengths distributions [A] for Yb4CrGeg at 100.0(3) K with estimated standard deviations in parentheses .............................. 237 Bond lengths distributions [A] for Yb4CrGe3 at 100.0(3) K with estimated standard deviations in parentheses (continue from part I)...238 Crystal data and structure refinement data for Yb4FCG63 at 100.0(3) K ................................................................................. 239 Atomic coordinates (x104), Fourier components of the displacive modulation (x104) and equivalent isotropic displacement parameters (A2x104) for Yb4FeGeg at 100.0(3) K with estimated standard deviations in parentheses .................................................................. 240 Fourier components of the atomic thermal parameters modulation (x103) for Yb4FCGCg at 100.0(3) K with estimated standard deviations in parentheses .......... . .......................................................... 241 Fourier components of the occupational modulation for Yb4FCGCg at 100.0(3) K with estimated standard deviations in parentheses ......... 241 xii Table 6-13. Table 6-14. Table 6-15. Table 6-16. Table 6-17. Table 6-18(1). Table 6-18(II). Table 6-19. Table 6-20. Table 6-21. Table 6-22. Table 7-1. Table 7-2. Bond lengths distributions [A] for Yb4F€G€3 at 100.0(3) K with estimated standard deviations in parentheses .............................. 242 Crystal data and structure refinement data for Yb4CoGe3 at 100.0(3)K ...................................................................... 243 Atomic coordinates (x104), Fourier components of the displacive modulation (x104) and equivalent isotropic displacement parameters (A2x104) for Yb4CoGeg at 100.0(3) K with estimated standard deviations in parentheses ................................................... 244 Fourier components of the atomic thermal parameters modulation (x103) for Yb4CoGe3 at 100.0(3) K with estimated standard deviations in parentheses ..................................................................... 245 Fourier components of the occupational modulation for Yb4CoGe3 at 100.0(3) K with estimated standard deviations in parentheses ......... 245 Bond lengths distributions [A] for Yb4COGCg at 100.0(3) K with estimated standard deviations in parentheses .............................. 246 Bond lengths distributions [A] for Yb4CoGeg at 100.0(3) K with estimated standard deviations in parentheses (continue from part I)...247 Temperature dependent cell parameters for Yb4CrGeg_2 crystal. Temperature range of 15 — 90 K was measured at ANL and 100 — 300 K at NU ............................................................................ 277 Temperature dependent cell parameters for Yb4CrGe3_3 crystal. Temperature range of 15 — 90 K was measured at ANL and 100 — 300 K at NU ............................................................................ 278 Temperature dependent cell parameters for Yb4FeGe3 crystal. Whole temperature range was measured at NU279 Temperature dependent cell parameters for Yb4CoGe3 crystal. Temperature range of 15 — 90 K was measured at ANL and 100 - 300 K at NU ............................................................................ 280 Crystal data and structure refinement data for CeCu61n6 in [4/mmm and Immm space groups .......................................................... 305 Atomic coordinates (x 104) and equivalent isotropic displacement 2 3 parameters (A x 10) for CeCu61n6 in I4/mmm space xiii Table 7-3. Table 7-4. Table 7-5. Table 7-6. Table 7-7. Table 7-8. Table 7-9. Table 7-10. Table 7-11. Table 7-12. Table 7-13. Table 7-14. group306 Anisotropic displacement parameters (A2 x 103) for CeCu6In6 in 14/mmm space group. The anisotropic displacement factor exponent 2 2 2 11 12 takes the form: ~21: [h a* U + ...+2hka*b*U ]306 Atomic coordinates (x 104) and equivalent isotropic displacement 2 parameters (A x 10) for CeCu6In6 in Immm space group 307 Anisotropic displacement parameters (A2 x 103) for CeCu61n6 in Immm space group. The anisotropic displacement factor exponent takes the 2 2 2 11 12 form: -211: [h a"‘ U +...+2hka*b*U ]307 Crystal data and structure refinement data for NdCu6.;251n5.375 and SmCu61n6 ....................................................................... 308 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for NdCumzslnsms ................................................... 309 Anisotropic displacement parameters (A2 x 103) for NdCumzsInsms. The anisotropic displacement factor exponent takes the form: 2 2 2 11 12 21: [h a*U +...+2hka*b*U ]309 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for SmCu61n6 ............................................................ 310 Anisotropic displacement parameters (A2 x 103) for SmCu61n6. The anisotropic displacement factor exponent takes the form: - 2 2 2 11 12 27: [h a* U +...+2hka*b*U ]310 Crystal data and structure refinement data for GdCu6_071n5_93 and DyCu6.231n5_77 .................................................................. 31 I Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for GdCu6.07In5,93 ...................................................... 312 Anisotropic displacement parameters (A2 x 103) for GdCu6_o7In5_93. The anisotropic displacement factor exponent takes the form: - 2 2 2 ll 12 21:11: a* U +...+2hka*b*U ] ............................................. 312 Atomic coordinates (x 104) and equivalent isotropic displacement para- xiv Table 7-15. Table 7-16. Table 7-17. Table 7-18. Table 7-19. Table 7-20. Table 7-21. Table 7-22. Table 7-23. Table 7-24. Table 7-25. Table 7-26. 2 3 meters (A x 10 ) for DyCu6231n577 ...................................................... 313 Anisotropic displacement parameters (A2 x 103) for DyCu6,231n5_77. The anisotropic displacement factor exponent takes the form: 2 2 2 ll 12 21: [h a* U +...+2hka*b*U ] ............................................... 313 Crystal data and structure refinement data for HOCU6VHII‘15‘39 and EI‘CU6.23III5,77 .................................................................... 3 I4 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for HoCuéulnsgg ...................................................... 315 Anisotropic displacement parameters (A2 x 103) for HoCuanlnsgg. The anisotropic displacement factor exponent takes the form: - 2 2 2 11 12 21: [h a* U +...+2hka*b*U ]315 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for ErCu6_23In5,77 ....................................................... 316 Anisotropic displacement parameters (A2 x 103) for ErCu6_23In5,77. The anizsotzropic displacement factor exponent takes the form: - 2 11 12 21: [h a* U +...+ 2hka*b*U ] .............................................. 316 Crystal data and structure refinement data for YbCu61n6 and YbAgs, 181116.83 ................................................................... 3 I7 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for YbCu61n6 ............................................................ 318 Anisotropic displacement parameters (A2 x 103) for YbCu61n6. The anisotropic displacement factor exponent takes the form: - 2 2 2 ll 12 21: [h a"' U +...+2hka*b*U 1 ............................................. 318 Atomic coordinates (x 104) and equivalent isotropic displacement para- 2 3 meters (A x 10 ) for YbAg5,.gIn6_33 ...................................................... 319 Anisotropic displacement parameters (A2 x 103) for YbAg513111633. The anisotropic displacement factor exponent takes the form: - 2 2 2 11 I2 21: [h a* U +...+ 2hka*b*U ]319 Summary of the crystallographic agreement factors and refinement XV Table 7-27. Table 7—28. Table 7-29. Table 7-30. statistics of the powder data for the different models .................... 320 Atomic coordinates and equivalent isotropic displacement parameters (A2) for the orthorhombic undistorted model .............................. 320 Atomic coordinates and equivalent isotropic displacement parameters (A2) for the orthorhombic distorted model #1 ............................. 321 Atomic coordinates and equivalent isotropic displacement parameters (A2) for the orthorhombic distorted model #2 ............................. 321 Atomic coordinates and equivalent isotropic displacement parameters (A2) for the tetragonal distorted model .................................... 322 xvi Figure 2-1. Figure 2-2. Figure 2-3 Figure 2-4. Figure 2-5. Figure 2-6. Figure 2-7. Figure 2-8. Figure 2-9. Figure 2-10. Figure 2-11. LIST OF FIGURES Scanning Electron micrograph (SEM) images of flux-grown crystals of (A) Yb7Co4InGelz and (B) Dy7Co4InGe12 ................................... 35 The overall structure of Yb7C04InGe12 as viewed onto the a, b-plane. For clarity the bonds to the Yb atoms are not drawn ........................... 39 The octagonal, hexagonal and pentagonal rings and their interconnection to form the corresponding tunnels running down the c- axis......... ............................................................................................. 40 (A) Polyhedral view of the Yb7Co4InGe12 structure featuring the connectivity between Co-centered Ge tetragonal pyramids. (B) The polyhedra share Ge(2) comers to form squares. (C) Stacking of squares along the c-axis forming square tubes4l The coordination environment of the RE atoms. The coordination sphere cutoff is 3.4 A ............................................................ 42 (A) Temperature dependence of the molar susceptibility Xm (triangles) and inverse 1 / xm (circles) for Yb7Co4lnGelz with an applied field of 500 G. (B) Magnetization data for Yb7Co4InGen collected at 3 K .................................................................................. 46 (A) Temperature variation of the susceptibility x(M/H) for Dy7C04InGe12 with an applied field of 500 G. Inset shows the low temperature (0-40 K) data. (B) Magnetic moment data for Dy7Co4In6612 collected at 3 K ................................................ 48 XPS spectra of Yb 4d core level for Yb7Co4InGeI2 at 300 K ............ 49 Lm absorption edge spectra of Yb in Yb7Co4InGe12 at 15 K (dashed line) and 300 K (solid line) .......................................................... 51 Comparison of Yb7Co4InGe.2 (solid line) and szO3 (dashed line) spectra at room temperature .................................................. 52 The Fourier Transform (FT) of the Yb XAFS for Yb4Co7InGe12 (15 K) compared with that for szO3 (RT). The FT’s are not corrected for photo-electron phase shifts. The k—range of the FT was 3-10 A"I ........ 52 xvii Figure 2-12. Figure 2-13. Figure 3-1. Figure 3-2. Figure 3-3. Figure 3-4. Figure 3-5. Figure 3-6. Figure 3-7. Figure 3-8. Figure 3—9. Figure 3-10. Figure 3-11. Lm absorption edge spectra of Yb in Yb7Ni4InGe.2 at 18 K (dashed line) and 295 K (solid line) .......................................................... 53 Variable temperature single-crystal resistivity data for Yb7Co4InGe12 at zero field. Inset: displays the low temperature resistivity data at 0, l and 5 T field .......................................................................... 54 Scanning Electron micrograph (SEM) image of a flux—grown Dy4CoInGe4 rod-shaped crystal .............................................. 70 The overall structure of Dy4CoInGe4 as viewed down the b-axis. For clarity the bonds to the Yb atoms are not drawn ........................... 74 The principal building unit the repetition of which makes up the whole [CoInGe4] network ............................................................. 75 Projection of the [ColnGe4] network roughly onto the a,b-plane. The RE atoms were removed to emphasize the connectivity ....................... 75 Twelve-membered rings and their interconnection to form the corrugated channels. The RE atoms were removed to emphasize the connectivity ....................................................................... 76 (A) Projection of the a,c-view of Dy4CoInGe4 (B) the a,b-view of Dy7Co4InGe12 and (C) the a,c—view of Dy4NizlnGe4 structures are displayed for comparison ..................................................... 77 Coordination environment of the Dy(1), Dy(2), Dy(3) and Dy(4) atoms. The coordination sphere cutoff is 4.0 A ..................................... 78 Polyhedral representation of the Dy4CoInGe4 structure featuring the connectivity of the Co-centered tetrahedra and In(1),In(2)-centered planar squares as viewed in the a,c-plane ................................... 80 Stacking of the Co-centered tetrahedra and In(l)-centered planar squares along the b-axis. The tetrahedral are fused, forming zigzag columns that extend down the b-axis ......................................................... 81 Temperature dependence of the molar susceptibility Xm(T) and inverse susceptibility l/Xm(T) of randomly oriented single crystals for Dy4CoInGe4 collected with an applied field of 500 G. Inset shows the low temperature data of the susceptibility Xm(T) ........................... 86 Temperature dependence of the molar susceptibility Xm(T) of Dy4CoInGe4 on single crystals randomly oriented with applied fields of 100 G, 500 G and 1000 G ..................................................... 87 xviii Figure 3-12. Figure 3-12. Figure 4-1. Figure 4-2. Figure 4-3. Figure 4-4. Figure 4-5. Figure 4-6. Figure 4-7. Figure 4-8. Figure 4-9. Low temperature (0 — 100 K) variation of xm of Dy4CoInGe4 at applied fields of 100, 500 and 1000 G in order to emphasize the magnetic transitions ......................................................................... 88 Magnetization curves of Dy4CoInGe4 collected at 3 K (solid line) 18 K (dotted line) and 60 K (dashed line). Inset shows the magnetization curve at 18 K in the positive fields area. The arrow indicates the metamagnetic transition ........................................................ 89 Scanning electron micrograph (SEM) image of (A) a flux-grown Yb3AuGezln3 single crystal and (B) a compact piece of YbAuIn ...... 106 The overall structure of Yb3AuGe21n3 as viewed onto the a, b-plane. For clarity the bonds to the Yb atoms are not drawn .......................... 110 (A) Projection of the crystal structure of Yb3AuGe21n3, viewed approximately down the b-axis, where the alternating layers of [Ge21n3] and [Yb3Au] are emphasized. (B) Projection of the [0621113] layer onto the a,b-plane. (C) Projection of the [Yb3Au] layer onto the a,b-plane. The Yb atoms are connected with lines in order to emphasize the comer-sharing triangles ...................................................... 11 1 Coordination environment of the Au, Ge, In and Yb atoms. The coordination sphere cutoff is 3.5 A ......................................... 112 Polyhedral view of the Yb3AuGe21n3 structure featuring the connectivity of the Au-centered In trigonal prisms and the Ge-centered In planar trigons, in the a, b-plane ...................................................... 113 Stacking of the Ge-centered In trigonal planes and Au-centered In trigonal prisms along the c-axis. The In trigonal prisms are fused, forming trigonal columns that extend down the c-axis .................. 113 (A) Temperature dependence of the molar susceptibility gm of Yb3AuGe21n3 (ground samples) with an applied field of 500 G. The inset shows the plot of 1/ (pm - )(0) versus temperature. (B) Magnetization data of Yb3AuGe21n3 collected at 3 and 150K .......... 116 Temperature dependence of the molar susceptibility Xm of Yb3AuGe21n3 (sample of randomly riented crystals) with an applied field of 1 kG. The inset shows the magnetization data of the same sample collected at 3 K and with fields sweeps from -50 to 50 kG ................................. 118 Temperature dependence of the molar susceptibility xm of Yb3AuGe21n3 on single crystals, oriented with the c-axis parallel (circles) and normal xix Figure 4-10. Figure 4-1 1. Figure 4-12. Figure 4-12. Figure 4-13. Figure 4-14. Figure 4-15. Figure 4-16. (rhombi) to the applied field of 2 kG ....................................... 119 Field dependence magnetization measurements for both parallel and normal orientations measured at 5 K between -50 and 50 kG of applied fields ............................................................................. 120 (A) Temperature dependence of the molar susceptibility xm of Yb3AuGe21n3 with an applied field of 0.5 kG and with a temperature rate of 10 K / min for both initial cooling down from RT and collecting data (A) for a sample of randomly oriented crystals. Inset shows higher temperature data and (B) xm(T) of the same sample after grinding it inside a nitrogen filled glove-box ............................................ 122 Magnetization data of Yb3AuGezln3 collected at 2 K and field sweeps between -55 and 55 kG (A) for a sample of randomly oriented crystals and (B) same sample after grinding inside a N2 filled glove-box. Inset shows low field data, where arrow indicates a metamagnetic like transition ........................................................................ 124 (C) Low field magnetization data of the ground inside the glove box Yb3AuGezln3 sample. The arrow indicates a metamagnetic like transition ......................................................................... 125 Temperature dependence of the molar susceptibility x,“ of Yb3AuGe21n3 with an applied field of 0.5 and l kG and temperature rates of 10 K / min (fast cooling) and 1 K / min (very slow cooling) (A) for a sample of randomly oriented crystals (B) same sample after grinding inside a nitrogen filled glove-box ..................................................... 128 Magnetization data of Yb3AuGe21n3 collected at 2, 65 and 200 K and with a temperature rate of 1 K / min (A) for a sample of randomly oriented crystals (B) same sample after grinding inside a nitrogen filled glove-box. Inset shows low fields region .................................. 130 Temperature dependence of the molar susceptibility )(m of a ground in open air YbAuIn sample, with an applied field of 1.8 kG. The inset shows the magnetization data of the same sample collected at 2 K and with field sweeps from -55 to 55 kG ....................................... 132 (A) Temperature dependence of the molar susceptibility Xm of Y‘bAuIn of a ground sample and hit pieces one, with applied fields of 1 and 1.5 kG, respectively and fast cooling. Inset shows low temperature data for pieces sample (B) Magnetization data of both samples collected at 2 K and field sweeps between -55 and 55 kG. Inset shows low positive fields region ........................................................................... 135 XX Figure 4-17. Figure 4-18. Figure 4-19. Figure 4-20. Figure 4-21. Figure 4-22. Figure 4-23. Figure 4-24. Figure 4-25. Figure 4-26. Figure 4-27. Figure 4-28. Temperature dependence of the molar susceptibility of a sample consisting of randomly oriented pieces for fast and slow cooling rates with 1 kG applied field ....................................................... 137 Temperature dependence of the molar susceptibility xm of YbAuIn sample after it was ground once (slightly) for fast and slow cooling and reground for second time (harder) for slow cooling. The applied field was 1 kG for all measurements ............................................. 138 Temperature dependence of the molar susceptibility )(m of a ground sample of YbAuIn of (A) ZFC, FC and F CW modes at l kG field (slow / fast cooling) and (B) curves in (A) and additional F C / F CW modes at 50, 150, 250 and 500 G fields ............................................... 140 Temperature dependence of the molar susceptibility Xm of a ground sample of YbAuIn and after pressing it into a pellet for ZFC, FC and FCW modes at 1 kG applied field and after fast cooling ................ 141 Temperature dependence of the molar susceptibility gm of YbAuIn of a sample of compact pieces with crystals approximately oriented with c- axis parallel to the applied fields of 1 and 5 kG for fast and slow cooling temperature rates .............................................................. 143 Comparison of fast/slow cooling magnetization data at various temperatures for the YbAuIn sample of compact pieces with crystals approximately oriented with c-axis parallel ............................... 145 Comparison of slow cooling magnetization data at various temperatures for YbAuIn sample of compact pieces with crystals roughly oriented with c-axis parallel to applied fields ....................................... 147 Schematic picture of the hypothetical accumulation of spins forming small ferromagnetic domains ................................................ 149 Lm absorption edge spectra of Yb in Yb3AuGezln3 at 295 K (dashed line) and in YbAuIn at 300 K (solid line) ................................. 152 Temperature variation of the electrical resistivity p(T) of Yb3AuGe21n3 from 2.48 to 302.3 K. The dashed line is a fit of the experimental data (squares) to the Bloch — Grt'rneisen - Mott formula (2). The inset displays the p(T) data for zero applied field (empty squares) and for 6 T applied field (solid trigons) for T < 100 K ................................. 154 Temperature variation of the electrical resistivity p(T) of YbAuIn from 4.2 to 274.3 K and at zero applied field .................................... 155 The temperature dependence of the thermoelectric power (TEP) of xxi Figure 4-29. Figure 4-30. Figure 5-I-l. Figure 5-I-2. Figure 5-1-3. Figure 5-1-4. Figure 5-1-4. Figure 5-1-5. Figure 5-1-6. Figure 5-1-7. Figure 5-I-8. Figure 5-1-8. Yb3AuGe21n3 measured in the temperature range of 310 — 700 K. 156 Heat capacity (Cp) of Yb3AuGe21n3 measured from 1.8 to 50.3K. The experimental data (circles) are fitted with Debye formula (2) (solid line) .............................................................................. 157 Heat capacity (CD) of YbAuIn measured from 1.8 to 50.3K. The experimental data (circles) are fitted with Debye formula (2) (solid line) .............................................................................. 158 Scanning Electron micrograph (SEM) images of flux-grown single crystals as well as aggregates of CeAuGeIn crystals ..................... 179 The overall structure of CeAuGeIn as viewed approximately onto the b, c-plane. For clarity the bonds to the Ce atoms are not drawn... ......182 The overall structure of CeAuGeIn as viewed approximately down the c-axis. For clarity the bonds to the Ce atoms are not drawn ............ 182 (A) Projection of the [AuIn]: PbO-type layer onto the a,c-plane, (B) a rotated view of the [AuIn] slab where the puckered form of the layer is emphasized ..................................................................... 183 (C) an alternative view of [AuIn] layer where the square Ge sheets are highlighted ..................................................................... l 83 Coordination environment of the crystallographically unique Ce atom. The coordination sphere cutoff is 3.65 A .................................. 183 (A) Polyhedral b, c-view of the CeAuGeIn structure, featuring the three- dimensional network of condensed distorted Au-centered In4Ge square pyramids and Ge zigzag chains and (B) details of the pyramids connectivity. One pyramid polyhedron has clear faces for clarity. . . 1 84 Temperature dependence of the molar susceptibility Xm(T) of CeAuGeIn measured on single crystals randomly oriented with applied fields of 0.3 kG and 1 k0 .................................................................. 186 (A) Field variation of the magnetization of CeAuGeIn collected at 2, 8, 11 and 60 K .................................................................... 188 (B) Magnetization curve at 2 K at low fields (0 — 22 kG) emphasizing the metamagnetic transition, indicated by the arrow. The solid line indicates a linear behavior of M(H) below the metamagnetic transition at HC = 3 kG .................................................................... 189 xxii Figure 5-1-9. Figure 5-I- 10. Figure 5-1- 11. Figure 5-II-l. Figure 5-II-2. Figure 5-II-3. Figure 5-II-4. Figure 5-II-5. Figure 5-11-6. Figure 5-II-7. Figure 6-1. Figure 6-2. Temperature dependence of the susceptibility M/H of CeAuGeIn measured on a compact piece composed of several crystals oriented with applied fields of 5 and 50 G (A) parallel to b-axis and (B) perpendicular to b-axis ....................................................... 191 Temperature variation of the electrical resistivity p(T) of CeAuGeIn from 1.58 to 35 K with applied fields of 0, 1, 2, 3 and 4 Tesla along the b-axis. The inset displays the [1(7) data for zero applied field for a temperature range of 1.58 — 108 K .......................................... 193 Lm-edge absorption spectra of Ce in CeAuGeIn at 16 K (solid line) and 300 K (dashed line). The spectrum of CeOz at 16 K (dotted line) is also given for comparison ......................................................... 195 Scanning Electron micrograph (SEM) images of flux-grown EuAuGeInz crystals .......................................................................... 205 The overall structure of EuAuGeInz as viewed approximately onto the a, c-plane. For clarity the bonds to the Eu atoms are not drawn, and only Ge(l) and Au(2) are shown for the two mixed-occupied sites of Au(l)/Ge(1) and Au(2)/Ge(2), respectively ............................... 209 (A) Projection of the [AuGelnz]: PbO-type layer onto the a,b-plane, (B) a rotated view of the [AuGeInz] slab where the puckered form of the layer is emphasized ........................................................... 209 (A) Eu atoms layer as viewed approximately in the a, c-direction. Eu—Eu bonds are drawn to emphasize the Eu atoms arrangement within the layers. (B) Coordination environment for the Eu atom out to 3.7112 A ................................................................................. 210 Polyhedral a,c-view of the EuAuGeInz structure featuring the interconnection of layers consisting of condensed In-centered Au(2)2Ge(1)2 tetrahedra ...................................................... 21 1 The overall structure of CeAuGeIn as viewed onto the b, c-plane and the overall structure of EuAuGeInz as viewed onto the a,c-plane .......... 213 Temperature dependence of the susceptibility M/H of EuAuGelnz measured on randomly oriented crystals with applied fields of 1 G for the ZFC mode (solid rhombi) and 10 G for the FC mode (open circles) .......................................................................... 214 Scanning Electron micrograph (SEM) images of flux-grown crystals of (A) Yb4CrGe3, (B) Yb4FeGe3 and (C) Yb4COGCg ......................... 251 The overall sub-structure of Yb4CrGe3 as viewed approximately onto xxiii Figure 6-3. Figure 6-4. Figure 6-5. Figure 6-6. Figure 6-7. Figure 6-8. Figure 6-9. Figure 6-10. Figure 6-11. the b, c-plane. For clarity the bonds to the Yb atoms are not drawn. ...254 The overall sub-structure of Yb4CrGe3 as viewed approximately down the c-axis. For clarity the bonds to the Yb atoms are not drawn ........ 255 (A) Projection of a fragment of the [er/4Ge(2)2]: PbO-type layer onto the a,c-plane (B) a rotated view of the [Cry/4Ge(2)2]: slab where the puckered form of the layer is emphasized ................................. 255 (A) Projection of a fragment of a modulated a,c-layer for Yb4CrGeg. Everything with less than 20% occupancy is plotted as a vacancy. The bond distance cutoff is 2.7 A. (B) a rotated view of the a, c-plane where the puckered form of the layer is emphasized ............................. 256 (A) Projection of a fragment of a modulated a,c-Iayer for Yb4FeGeg. Everything with less than 20% occupancy is plotted as a vacancy. The bond distance cutoff is 2.7 A. (B) a rotated view of the a, c-plane where the puckered form of the layer is emphasized ............................. 257 (A) Projection of a fragment of a modulated a,c-layer for Yb4CoGe3. Everything with less than 20% occupancy is plotted as a vacancy. The bond distance cutoff is 2.7 A. (B) a rotated view of the a, c-plane where the puckered form of the layer is emphasized ............................. 258 The modulated Ge square net, described with Ge-Ge dimmers in Yb4CrGe3. The Ge-Ge bonds were drawn within the cutoff distance of 2.7 A. The parallel to the bonds numbers represent the Ge-Ge dimer bond lengths, whereas the horizontal numbers represent other Ge-Ge distances ........................................................................ 259 The modulated Ge square net, described with Ge-Ge dimmers in Yb4FeGe3. The Ge—Ge bonds were drawn within the cutoff distance of 2.7 A. The parallel to the bonds numbers represent the Ge-Ge dimer bond lengths, whereas the horizontal numbers represent other Ge-Gc distances ........................................................................ 260 The modulated Ge square net, described with Ge-Ge dimmers in Yb4CoGeg. The Ge-Ge bonds were drawn within the cutoff distance of 2.7 A. The parallel to the bonds numbers represent the Ge-Ge dimer bond lengths, whereas the horizontal numbers represent other Ge-Ge distances ........................................................................ 261 (A) Temperature dependence of the molar susceptibility Xm(T) of Yb4CrGeg with an applied field of l kG. Inset shows the inverse susceptibility l/xm(T) data. (B) Field variation of the magnetization of Yb4CI‘GCg collected at 5 K ................................................... 265 xxiv Figure 6-12. Figure 6-13. Figure 6-14. Figure 6-15. Figure 6-16. Figure 6-17. Figure 6-18. Figure 6-19. Figure 6-20. Figure 6-21. Figure 6-22. Figure 6-23. Figure 6-24. (A) Temperature dependence of the molar susceptibility xm(T) and inverse susceptibility l/xm(T) of Yb4FCG€3 with an applied field of 600 G. (B) Low temperature data of Xm(T), where arrows indicate possible transitions ...................................................................... 266 (A) Field variation of the magnetization of Yb4FeGeg collected at 2 K. (B) Temperature dependence of the susceptibility M/H of Yb4FeGeg measured on randomly oriented crystals with an applied of field of 10 G for ZF C mode and for FC mode ............................................. 267 Yb Lm-edge absorption spectra of Yb4CI‘GCg at 15, 100 and 300 K...269 Yb Lin-edge absorption spectra of YbrFeGeg at 30, 80, 160 and 300 K ................................................................................. 270 Yb Lm-edge absorption spectra of Yb4CoGeg at 30, 80, 160 and 300 K ................................................................................. 271 Difference plots for Yb4CrGe3 generated by subtracting the data taken at 100 and 300 K from the 15 K data .......................................... 272 Difference plots for Yb4FeGeg generated by subtracting the data taken at 80, 160 and 300 K from the 30 K data ..................................... 273 Difference plots for Yb4CoGeg generated by subtracting the data taken at 80, 160 and 300 K from the 30 K data .................................. 274 Temperature dependence of a,b,c cell axes for (A) Yb4CrGeg_2 and (B) Yb4CrGeg_3 single crystals. Temperature range 15 — 90 K measured at ANL and 100 — 300 K at NU ................................................ 281 Temperature dependence of the cell volume for Yb4CrGeg_2 and Yb4CrGeg_3 crystals. Temperature range 15 - 90 K measured at ANL and 100 — 300 K at NU ....................................................... 282 Temperature dependence (A) of a,b and c cell axes and (B) of cell volume for an Yb4FeGe3 single crystal. Whole temperature range 10 — 320 K measured at NU ....................................................... 283 Temperature dependence of (A) cell volume and (B) a,b and c cell axes for an Yb4CoGeg single crystal. Temperature range 15 — 90 K measured at ANL and 100 — 300 K at NU ............................................. 284 Heat capacity (Cp) for Yb4CrGeg measured from 2.96 to 50.8 K. The experimental data (circles) are fitted with Debye formula (1) (solid XXV Figure 6-25. Figure 7-1. Figure 7-2. Figure 7-3. Figure 7-4. Figure 7-5. Figure 7-6. Figure 7-7. Figure 7-8. Figure 7-9. Figure 7-10. Figure 7-11. Figure 7-12. Figure 7-13. line) .............................................................................. 286 Temperature variation of the electrical resistivity p(T) of Yb4FeGe3 from 2.28 to 301.75 K with at zero applied field ................................ 288 High resolution powder X-ray diffraction pattern for CeCu61n6 ........ 304 Scanning electron micrographs of flux-grown crystals of (A) typical NdCu6,1251n5,375 (B) SmCu61n6 and (C) YbAg5ngn633, respectively. . .324 The overall structure of ErCu6_z3In5,77 as viewed onto the b, c-plane. For clarity the bonds to the Er atoms are not drawn ........................... 327 The corrugated Cu layers running parallel to the c-axis ................. 328 [010] projection of the Cu net along the b-axis ........................... 328 Projection of the layer of In cages and Er atoms in approximately the a,c plane .............................................................................. 329 The In-Cu polyhedral cage hosting the Er atom .......................... 329 Polyhedra representation of the ErCu6231n577 structure .................. 330 The variation of RECu(,+,,In6.x unit cell volume across the rare-earth series ............................................................................ 330 (A) Temperature dependent magnetic susceptibility xm(T) and its inverse l/xm(T) for CeCu6In6 measured with an applied field of 2 kG. (B) Field dependent magnetization measured at 3 K for CeCu61n6. . ..3 32 (A) Temperature dependent magnetic susceptibility xm(T) and inverse l/xm(T) data for NdCu6,.251n5,375 measured with 1 kG of applied field. (B) Field dependent magnetization measured at 3 K for NdCu6_.251n5,375 ................................................................................... 334 (A) Temperature dependent magnetic susceptibility xm(T) data for SmCu61n6 measured with an applied field of 0.5 kG. (B) Field dependent magnetization data measured at 2 K for SmCu61n6 ......... 336 (A) Temperature dependent magnetic susceptibility xm(T) data for GdCublnr, measured with an applied field of l kG. (B) Field dependent magnetization data measured at 2 K (solid triangles) and 300 K (open circles) for GdCu61n6 ......................................................... 338 xxvi Figure 7-14. Figure 7-15. Figure 7-16. Figure 7-17. Figure 7-18. Figure 7-19. Figure 7-20. Figure 7-21. (A) Temperature dependent magnetic susceptibility xm(T) and its inverse l/Xm(T) for DyCu6_23In5,-;7, measured at 1 kG field. (B) Field dependent magnetization at 3 K for DyCu623In577. The arrow indicates the reorientation of the spins ................................................ 340 (A) Temperature dependent magnetic susceptibility Xm(T) and inverse l/Xm(T) data for HoCudulnsgg measured with 1 k6 of applied field. (B) Field dependent magnetization data measured at 2 K (open circles) and 300 K (solid rhombi) for HOCU6J 11115.39. Inset: shows data at 300 K up to 35 kG of field. Inset: shows data at 300 K upto 35 kG of field. . .......342 (A) Temperature dependent magnetic susceptibility xm(T) and its inverse I/Xm(T) for ErCu6_23In5.77. Inset: shows the antiferromagnetic peak at 3.5 K. (B) Field dependent magnetization at 2 and 10 K for ErCu6,23In5_77 ................................................................... 344 (A) Temperature dependent magnetic susceptibility Xm(T) data for YbCu61n6 measured with applied fields of 0.6 kG (triangles) and 3 kG (circles). (B) Field dependent magnetization data measured at 2 K for YbCu61n6 ....................................................................... 346 (A) Temperature dependent magnetic susceptibility me) and inverse l/xm(T) data for YbAg5ngn633 measured with an applied field of 2 kG. (B) Field dependent magnetization data measured at 2 K for YbAg5_13In6,g3 .................................................................. 348 Lm-edge absorption spectra of Ce in CeCu61n6 at 16 K (solid line) and 300 K (dashed line). The spectrum of CeOz at 16 K (dotted line) is also given for comparison ......................................................... 351 LII-edge absorption spectra of Yb in YbCu61n6 at 16 K (solid line) and 295 K (dashed line). The spectrum of CeOz at 16 K (dotted line) is also given for comparison ......................................................... 352 Lm-edge absorption spectra of Yb in YbAg61n6 at 18 K (solid line) and 295K(dashedIine)........................ ................................... 353 xxvii CHAPTER 1 Introduction l-l. Introduction to Intermetallics, Selected Properties and Applications Solid state chemistry is a multidisciplinary field that deals with the synthesis, structural determination and physical properties characterization of various solids, and it has been playing an increasingly significant role in the design and preparation of new advanced materials. Solid state compounds have been the foundation of the electronics industry for many years and contribute extensively in many other emerging technologies, such as microelectronics, nonlinear optics, superconductivity, thermoelectric and photovoltaic energy conversion and storage, nanotechnology, advanced ceramics, information packaging and aerospace applications.HO Intermetallic compounds consist one of the oldest and largest class of solid state materials. The evolution of interrnetallic compounds can be traced back to ancient times (e.g. arnagalm use, Cu4Hg, Angg3, for dental applications)H but the recognition of their existence and some basic study of their physical properties started only in 1839,]2 and it took more than a century for the first systematic investigation results to be reported.”'4 During that time an increasing number of binary and ternary compounds were found and considerable efforts were made in an attempt to establish the rules relating to the stability of different phases. Thus interrnetallics had come into focus as high-performance materials.l3 Ever since a growing attention to these metallic compounds has been given by both pure and applied materials scientists and has resulted in the discovery of a vast variety of intermetallic compounds that exhibit numerous structures'5 and a wealth of interesting physico-chemical and mechanical properties. ' "'6‘ I 7 A class of such materials the interrnetallic tetrelides (Si, Ge, Sn) are both scientifically and technologically important. They are the subject of continuous interest because of their intrinsic properties such as hardness, chemical stability, high melting points18 and superconductivity4 and they found intriguing applications including high- temperature structural materials,‘9 high-T furnaces,‘8 high-T coatings20 and thermoelectric energy conversion.3 A notable compound is the M0812 and its alloys, which combines very high melting point, low density and outstanding oxidation resistance and finds applications such as electronic devices, heating elements, energy conversion devices, glass melting and other.” Intermetallic compounds are like any other compound that is they have precise proportions of two or more metallic elements (or metalloids) that form periodic crystalline solids with different structures from those of the component elements. They should not be confiised with the conventional metal alloys, as they differ greatly. An interrnetallic compound is a chemical compound that has a definite atomic formula, with a fixed or narrow range of chemical composition. An example is the binary Ni3A12. Conventional alloys, on the other hand, comprise a homogeneous solid solution or a multiphase mixture of one or more metals, with randomly distributed atoms (disordered) and without having any particular chemical formula. Essentially, they consist of a base material to which certain percentages of other elements have been added as in the case of the very well-known stainless steel, an alloy with a composition of Fe-l 8%Cr-8%Ni. Another significant difference between the two types of materials is also the way the atoms are connected. In the conventional alloys, the atoms are connected with weak metallic bonds and the electrons freely move amongst the atoms (good conductors). On the contrary, in interrnetallics the bonds can be metallic but they can also be partly ionic or covalent, and therefore stronger. The stronger bonding and the high degree of ordering as the individual atoms occupy preferred positions within the crystal lattice, leads to the characteristic mechanical properties of intermetallics. Crystal structures of interrnetallic compounds vary significantly with the particular combination of constituent elements in them and in turn, the physical and chemical properties of interrnetallic compounds depend strongly on the adopted structures. The formation of a particular structure is largely because the bonding between unlike atoms is often stronger than between like atoms. The result is an ordered atom distribution where atoms are preferentially surrounded by unlike atoms. In the past, various criteria, models, rules, and theories based on atomic size effects, electronic effects and electronegativity had been developed in order to explain the nature of the complex relationship between structure types and the kinds of the combining metal atoms.'3 However, despite the great effort to rationalize the rules governing the existence of the huge number of intennetallic phases there is still a great difficulty in fiilly understanding the compositions, bonding and assignment of oxidation states for individual atoms. Due to the vast diversity of the interrnetallic phases and their behaviour, it is a very difficult task to classify them into groups and it is even harder to try and generalize their properties. Nonetheless, there are some fundamental properties that can be roughly observed in every group: high melting point, high hardness, high wear resistance, low ductility and good oxidation or corrosion resistance in many cases. These properties make the intermetallics exceptional materials for structural, heat resistant and corrosion resistant applications.17 However, some intermetallics, mainly polycrystalline ones, are brittle at room temperature and this is the main obstacle to structural applications. For that reason many attempts have been made to improve their properties through structural modification, for example, by adding ternary elements into mother compounds. This is why the prediction of crystal structures is indeed a first step to the successful design of intermetallic compounds. Furthermore, many intermetallic materials are widely used in many other technological applications such as electronic, magnetic and battery applications'7 due to their important physical properties such as superconductivity and permanent magnetism,“22 shape memory effects (mainly NiTi, NiAl, CuZn),23‘24 catalytic activity25 as well as lithium and hydrogen storage capacity.”28 It can thus logically concluded that intermetallic compounds are useful materials and marks the importance of developing and utilizing low temperature and practical methods for their synthesis. 1-2. Motivation for the Use of Molten Metal Fluxes as Synthetic Media The majority of the melting points of the starting materials employed in the synthesis of intermetallics such as the rare earth metals, the transition metals and some main group elements are generally over 1000 °C. The melting points of some examples are 1407 0C for Dy, 1072 °C for Sm, 1875 °C for Cr, 1495 °C for Co, 2500 °C for Ru, 1410 0C for Si. For this reason, intermetallic compounds have been traditionally prepared through high temperature methods (often > 1500 °C) usually by means of techniques such as arc-melting, induction heating or powder metallurgy. This is required to facilitate the solid-state diffusion of the high melting solids involved.29 Such reaction conditions, combined with long annealing times and frequent regrinding steps for powder preparations, are often necessary to overcome the limitations of solid-solid diffusion. The synthetic conditions, presented above, lead to two important limitations. Such high temperature reactions generally afford the most thermodynamically stable phases (usually simple binary or ternary compounds) which frequently prevent the exploration of possible complex phases that could be more kinetically stable. At the same time, the fast overall reaction times involved in these reactions and the frequent regrinding steps in some cases, normally result in microcrystalline products which limit their accurate structural and physical characterization, especially if they are anisotropic in nature. A variety of techniques have been developed to overcome the limitations inherent in this traditional approach and yield intermetallics at lower temperatures. Examples of low temperature approaches include solvothermal techniques,3O high-energy ball milling,31 electrodeposition,32 chemical vapor deposition (CVD), gas-phase condensation 33-35 and solution-mediated routes, and molten flux synthesis.”37 Particularly, crystal 38-42 41 ,43,44 growth employing metals or salts as fluxes has been known for a long time, while in recent years, the use of molten metals as solvents for the synthesis of new materials has attracted increasing attention36‘45'S4 The advantages of this method which uses an excess of a molten metal as a flux in which the reactant elements dissolve include enhanced diffusion of the reactants facilitated by the solvent and usually large, high- quality crystal growth directly from the solution. Additionally, the lower reaction temperatures allow better kinetic control and the trapping of kinetically stable phases, giving more flexibility to yield novel multinary compounds that are unattainable through traditional high temperature synthetic techniques. In the cases where the employed molten metal flux acts only as a solvent and is not included in the final product it is called a “non-reactive flux,” whereas when the flux element gets incorporated into the product compound it is characterized as a “reactive flux.” Nevertheless, in order for a metal to be a suitable flux for synthetic reactions several key conditions must be met. Firstly, the metal should melt at relatively low temperatures so it does not require the use of special containers or heating equipment while at the same time there should be a big difference between its melting and boiling point. Additionally, the solvent should dissolve sufficient amounts of the solutes and it should not react with them to form stable binary phases that could prevent the formation of the desired product. Finally, the excess metal should be easily removed by means of chemical or mechanical methods from the final products. 1-3. Use of Molten AI, Ga and In for the Exploratory Synthesis of Rare Earth Transition Metal and Tetrel Containing Intermetallic Compounds Under the above mentioned criteria the group III elements (mainly Al, Ga, and In) constitute excellent candidates for use as liquid synthetic media. In the past few decades, our group, as well as others, has investigated the use of molten Al and Ga which has proven invaluable for exploring new intermetallic systems. Particularly, Al melts at 660 °C while it has a boiling point of 2792 °C. Additionally, inspection of the Al-containing alloy phase diagram directly reveals the large number of compounds that are soluble in molten Al,55’56 whereas the excess of aluminum can be easily removed from the products by submersion in a base solution of NaOH. Investigations of molten Al in the system RE/TM/Al (where RE = rare earth metal and TM = transition metal) by Jeitschko and his coworkers resulted in numerous ternary compounds, where AI principally acts as reactive flux and produces often Al-rich products.“62 Our group has recently initiated a project where molten Al is used to investigate the reactivity of the quaternary systems RE/TM/Al/Si or Ge (RE = rare earth metal, TM = transition metal) which readily gave rise to new complex quaternary phases with some adopting new structure types or exhibiting interesting magnetic propertiesté Some examples include the szNi(Si.-xNix)A148i6,°7 REgRu12A1498i968 and REzNiAlaGe269 compounds. In these cases, notable features revealed from this chemistry is the inclusion of Al into the crystal structure as well as the reducing ability of Al which allows it to reduce stable oxides such as perovskites MTiO3 (M = Ca, Sr, Ba) to intermetallic compounds, as it has be shown in the case of M3Au6+xA126Ti70 Furthermore, we observed that even though the Si and Ge in these systems exhibit parallel chemistry, however they do not always produce isostructural analogs. Similar explorations of the reactivity of Si and Ge in the system RE/Au/Al resulted in the homologous series of tetragonal compounds RE(AuA12),,A12(AuxSi..x)65 for Si while for Ge gave the rhombohedral REAuAlaGez and the tetragonal REAuAl4(AuxGei.x)2 families of compounds.7| The remarkable success observed in the systematic investigations of molten Al as a preparative tool for the synthesis of ternary and quaternary intermetallic phases led us to extend this research to Ga. Ga holds similar properties that make A1 such a viable synthetic flux. In particular, Ga has a quite low melting point of 29 0C and a high enough boiling point of 2200 °C. Furthermore, it readily dissolves Si and Ge without forming binary phases while it dissolves a number of rare earth and transition metals.56 Finally, it can be easily removed from the products by chemical or mechanical means. Interestingly, when Ga was employed in analogous reactions within the RE/TM/Si system as Al, generally yielded Ga-free products (e.g. SmNiSi3)72 or Si-free products (e.g. szNi3Si5 and szNiGalz).73‘74 This is in contrast with the corresponding A1 work where it was found that it is impossible to synthesize Al-free silicides. When Si is replaced by Ge in the Ga flux reactions however, quaternary compounds such as RE3Ni3GagGe375 and GdCol.,,Ga3Geg76 are readily observed. These are surprising differences in reactivity given the close relationship of Al to Ga and Si to Ge respectively. These results imply that there is much new chemistry and reactivity to be learned by studying fluxes of related elements. Upon this concept, we have recently expanded this work to also include molten In as a synthetic medium in parallel to Al and Ga systems. Indium possesses similar characteristics that make Al and Ga ideal metals for the flux technique, which are its low melting point at 156 °C and high boiling point at 2080 0C, it does not form binary phases with Ge or Si,77 and it’s easy to remove through mechanical or chemical means. Furthermore, In has the ability to dissolve Si, Ge and a host of lanthanide and transition metals, resulting in highly reactive forms of the elements. Indium flux, although it has been commonly used in the past for the crystal growth of primarily known binary and 78-83 ternary phases it has been less exploited as a synthetic tool for the discovery of new compounds compared to Al and Ga, particularly for quaternary phases, despite the most 84'8930 this area is relatively unexplored. Some of the intermetallic systems recent efforts, that have been prepared with liquid In by other groups are CeTIn5 and Celeng,82‘90‘9| YbTIn5,92‘93 REgCuzln80 and EuCu2Slz.94 Preliminary results from the synthetic investigations of molten In as a solvent in the system REfTM/Ge conducted by previous member of our group, Dr. J. R. Salvador, suggested that indium acts mainly as a non reactive flux with germanides in the same way that gallium acts as a non reactive flux with silicides. That work resulted in the new ternary germanides REZZn3Ge6 (RE = La, Ce, Pr, Nd) which exhibit near Zintl phase behavior95 and in the stabilization of a new B-form of the RENiGez (RE = Dy, Er, Tm, Yb, Lu) compounds that could only be synthesized exclusively from In flux.96 Additionally, the new ternary orthorhombic indides REAu21n497 were formed with the rare earth metals of La, Ce, Pr and Nd while Yb metal gave a different compound that has the same composition of YbAu21n4 but crystallizes in a monoclinic space group.98 Finally, afier careful experimental condition control the first quaternary compound in the system RE/TM/Ge/In, REaNizlnGea (RE = Dy, Ho, Er, Tm) was formed.99 The tremendous success of our systematic investigations of Al and Ga fluxes as well as the preliminary results of In, justifies the present work which constitutes an expansion of that research to include molten In as preparative tool for the discovery of new intermetallic compounds. The biggest part of this project represents the exploratory synthesis of novel quaternary compounds in the system containing a rare earth, a transition metal, germanium metal and indium metal. Intermetallic compounds of the ternary systems RE/TM/In and RE/TM/Ge include numerous new intermetallic phases that exhibit rich structural variety and interesting physical properties and have been extensively investigated in the last few decades.'5"00"04 Thus, our goal is to exploit the ability of liquid In as a reactive flux in the system RE/TM/Ge/In and discover new complex multinary compounds that could exhibit interesting structural features as well as chemical and physical properties. Additionally, by studying In/Ge systems analogous to Al/Ge and Ga/Ge ones could help us draw parallel and trends in this chemistry, which could further shed light in understanding the chemical reactivity of the systems as well as the composition, structure and properties of the resulting products. Under this scope, we have performed studies of the systems RE/Co/Ge/In, RE/Ni/Ge/In and RE/Au/Ge/In and we have succeeded in isolating a number of novel quaternary compounds. Results of the study of their structural features and physical behavior are discussed in chapters 2-5 of this work. Among intermetallics that are likely to be stabilized in metallic fluxes, we are particularly interested in the Ce and Yb-containing ones because they can display a wealth of intriguing properties which are associated with their valence instability.105 "06 Both RE ions can exhibit two electronic configurations that are closely spaced in energy: the magnetic Ce3+ (41') and the nonmagnetic Ce“ (4f 0) for Ce and the magnetic Yb3+ (4f3) and the nonmagnetic Yb2+ (41”) one for Yb. Due to this feature Yb is usually considered as the “f—hole” analogue of Ce. The intriguing physical phenomena that these compounds often exhibit include intermediate valence (IV) or valence fluctuating behavior, unusual magnetism, Kondo and heavy-fermion (HF) behavior and superconductivity.")Z'HM’W'IIl These properties are generally believed to arise from the strong hybridization (interaction) between the localized 4f electrons and the delocalized s,p,d conduction electrons.105 .112 Due to these phenomena that these materials may 10 display focus of the physical characterization of the compounds discovered in this project is placed in the magnetic properties and the Yb-, Ce-valency of the corresponding compounds which is studied with X-ray Absorption Near Edge Spectroscopy measurements (XANES). In our explorations of the systems Yb/TM/Ge/In we have also found the new ternary YbaTMGeg (TM = Cr, Fe, Co) compounds where In acted only as a solvent without being incorporated into the final product and are presented in Chapter 6. Finally, in Chapter 7 we present results of our studies of the ternary systems RE/Cu/In and RE/Ag/In. ll References: (1) Chen, G.; Dresselhaus, M. S.; Dresselhaus, G.; Fleurial, .I. P.; Caillat, T. International Materials Reviews 2003, 48, 45-66. (2) Datta, S. K.; Tewari, S. N.; Gatica, J. E.; Shih, W.; Bentsen, L. Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science 1999, 30, 175-181. (3) Rowe, D. M. CRC Thermoelectric Handbook CRC Press: Boca Raton, FL, 1995. (4) King, R. B. Inorg Chem. 1990, 29, 2164. (5) McCarthy, B. P.; Pederson, L. R.; Chou, Y.; Zhou, X. D.; Surdoval, W. A.; Wilson, L. C. Journal of Power Sources 2008, 180, 294-300. (6) Williams, M. C.; Strakey, J. P.; Surdoval, W. A.; Wilson, L. C. 2006, p 2039- 2044. (7) Gadow, R.; Kern, F .; Killinger, A. 2008, p 58-64. (8) Ivanov, E. Y.; Shapiro, A. 13.; Home, M. G. Welding Journal'2006, 85, 196$- 199$. (9) Liu, H. K.; Wang, G. X.; Guo, Z. P.; Wang, I. Z.; Konstantinov, K. Journal of Nanoscience and Nanotechnology 2006, 6, 1-15. (10) Kanatzidis, M. G.; Poeppelmeier, K. R. Prog. Solid State Chem. 2008, 36, l. (11) Sauthoff, G. Intermetallics; VCH: Verlagsgesellschaft, Weinheim, 1995. (12) Karsten, K. Annln. Phys. 1839, 46, 1960. (13) Westbrook, J. H. Intermetallic compounds; Wiley and Sons: New York, 1967. (14) Gschneidner, K.A. Rare earth alloys; Van Nostrand, 1961. 12 (15) Villars, P.; Calvert, L. D. "Pearson's Handbook of Crystallographic Data for Intermetallic Phases ", 2nd ed. ,' American Society for Metals OH 44073, 1991. (16) Fahnle, M.; Welsch, F. Physica B 2002, 321, 198. (17) Slotoff, N. S.; Liu, C. T.; Deevi, S. C. Intermetallics 2000, 8, 1313. (18) Fitzer, E. Plansee Proceedings 1955; Benesovsky, F. ed. London, 1956; Vol. Chapter 7. (19) Shah, D. M.; Berczik, D.; Anton. D. L.; Hecht, R. Mater. Sci. Eng. A. 1992, 155, 45. (20) Meier, G. H. ; Stoloff, N.S.; Koch, C.; Liu, C. T.; Izumi, O. In Materials Research Society Symposium Proceedings 81; Materials Research Society: 1987; Vol. 443. (21) Nagamatsu, J .; Nakagawa, N.; Muranaka, T.; Zenitani, Y.; Akimitsu, J. Nature 2001, 410, 63. (22) Sun, S.; Murray, C. B.; Weller, D.; Folks, L.; Moser, A. Science 2000, 28 7, 1989. (23) Cui, J.; Shield, T. W.; James, R. D. Acta Mater. 2004, 52, 35. (24) Stern, R. A.; Willoughby, S. D.; MacLaren, J. M.; Cui, J.; Pan, Q.; James, R. D. J. Appl. Phys. 2003, 93, 8644. (25) Casado-Rivera, E; Volpe, D. J.; Alden, L.; Lind, C.; Downie, C.; Vazquez- Alvarez, T.; Angelo, A. C. D.; DiSalvo, F. J.; Abruna, H. D. J. Am. Chem. Soc. 2004, 126, 4043. (26) Shi, L.; Li, H.; Wang, 2.; Huang, X.; Chen, L. J. Mater. Chem. 2001, 11, 1502. (27) Ronnebro, E.; Yin, J.; Kitano, A.; Wada, M.; Sakai, T. Solid State Ionics 2005, 176, 2749. (28) Mukaibo, H.; Osaka, T.; Reale, P.; Panero, S.; Scrosati, B.; Wachtler, M. J. Power Sources 2003, 132, 225. 13 (29) West, A.R. Solid State Chemistry and its Applications; Wiley: New York, N.Y., 1984. (30) Heibel, M.; Kumar, G.; Wyse, C.; Bukovec, P.; Bocarsly, A. B. Chem. Mater. 1996, 8, 1504. (31) Meitl, M. A.; Dellinger, T. M. ; Braun, P. V. AdV. F unct. Mater. 2003, 13, 795. (32) Martin-Gonzalez, M.; Prieto, A. L.; Knox, M. S.; Gronsky, R.; Sands, T.; Stacy, A. M. Chem. Mater. 2003, 15, 1676. (33) Sanchez-Lopez, J. C.; Gonzalez-Elipe, A. R.; Fernandez, A. J. Mater. Res. 1998, 13, 703. (34) Leonard, B. M.; Bhuvanesh, N. S. P.; Schaak, R. E. J. Am. Chem. Soc. 2005, 127, 7326. (35) Ung, D.; Soumare, Y.; Chakroune, N.; Viau, G.; Vaulay, M.-J.; Richard, V.; Rievet, F. Chem. Mater. 2007, 19, 2084. (36) Kanatzidis, M. G.; Pottgen, R.; Jeitschko, W. Angewandte Chemie-International Edition 2005, 44, 6996. (37) Fisk, Z.; Remeika, J. P. Handbook on the Physics and Chemistry of Rare Earths, 1989; Vol. 12. (38) Deitch, R. H. Crystal Growth; Pamplin, B. R. ed.; Pergamon Press: Oxford, New York, 1975; Vol. 100. (39) Lundstrom, T. J. Less-Common Met. 1984, 100, 215. (40) Canfield, P.C.; Fisk, Z. Philos. Mag. B 1992, 65, 1117. (41) Elwell, D.; Scheel, H. J. Crystal growth from high-temperature solution; Academic Press: London, New York, 1975. (42) Morelli, D.T.; Canfield, P.C.; Drymiotis, P. Phys. Rev. B 1996, 53, 12896. 14 (43) Kanatzidis, M. G.; Sutorik, A. Prog. Inorg. Chem. 1995, 43, 151. (44) Kanatzidis, M. G. Curr. Opin. Solid State Mater. Sci. 1997, 2, I39. (45) Schaefer, J.; Bluhm, K. Z. Anorg. Allg. Chem. 1994, 620. 1578. (46) Utzolino, A.; Bluhm, K. Z. Naturforsch., B: Chem. Sci. 1996, 51, 305. (47) DiSalvo, F. J. Solid State Commun. 1997, 102, 79. (48) Schluter, M.; Jeitschko, W. Inorg Chem. 2001, 40, 6362. (49) Williams, W.M.; Moldovan, M.; Young, DR; Chan, J.Y. J. Solid State Chem. 2005, I 78, 52. (50) Williams, W.M.; Macaluso, R.T.; Moldovan, M.; Chan, J .Y. Inorg Chem. 2003, 42, 7315. (51) Bauer, E.D.; Bobev, S.; Thompson, J.D.; Hundley, M.F.; Sarrao, J.L.; Lobos, A.; Aligia, A.A. J. Phys. Cond. Matter 2004, 16, 4025. (52) Bobev, 8.; To, P.H.; Thompson, J.D.; Hundley, M.F.; Sarrao, J.L.; Lobos, A.; Aligia, A.A. J. Solid State Chem. 2005, 178, 2091. (S3) Bie, H. Y.; Zelinska, O. Y.; Tkachuk, A. V.; Mar, A. Chemistry of Materials 2007, 19, 4613. (54) Tobash, P. H.; Meyers, J. J.; DiFilippo, G.; Bobev, S.; Ronning, R; Thompson, J. D.; Sarrao, J. L. Chemistry of Materials 2008, 20, 2151. (55) Hansen, M.; Anderko, K. Constitution of Binary Alloys; 2nd ed. McGraw-Hill, New York, 1958. (56) Massalski, T.B. Binary Alloy Phase Diagrams ASM, Metals Park, 1986. (57) Nierrnan, J .; Jeischko, W. Z Anorg. Allg. Chem. 2002, 628, 2549. 15 (58) Fehrmann, B.; Jeitschko, W. J. Alloys Compd. 2000, 298, 153. (59) Thiede, V. M. T.; Fehrmann, B.; Jeischko, W. Z. Anorg. Allg. Chem. 1999, 625, 1417. (60) F ehrmann, B.; Jeitschko, W. Inorg Chem. 1999, 38, 3344. (61) Reehuis, M.; Wolff, M.W.; Krimmel, A.; Scheidt, E.W.; Stusser, N.; Loidl, A.; Jeitschko, W. J. Phys. Cond. Matter 2003, 15, 1773. (62) Thiede, V.M.T.; Ebel, T.; Jeitschko, W. J. Mater. Chem. 1998, 8, 125. (63) Lattumer, S. E.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Chem. Mater. 2002, 14, 1695-1705. (64) Lattumer, S. E.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2003, 42, 7959-7966. (65) Lattumer, S. E.; Kanatzidis, M. G. Inorg. Chem. 2008, 47, 2089-2097. (66) Sieve, B.; Sportouch, S.; Chen, X. Z.; Cowen, J. A.; Brazis, P.; Kannewurf, C. R.; Papaefthymiou, V.; Kanatzidis, M. G. Chem. Mater. 2001, 13, 273. (67) Chen, X. Z.; Sportouch, S.; Sieve, B.; Brazis, P.; Kannewurf, C. R.; Cowen, J. A.; Patschke, R.; Kanatzidis, M. G. Chem. Mater. 1998, 10, 3202. (68) Sieve, B.; Chen, X. Z.; Henning, R.; Brazis, P.; Kannewurf, C. R.; Cowen, J. A.; Schultz, A. J.; Kanatzidis, M. G. J. Am. Chem. Soc. 2001, 123, 7040. (69) Sieve, B.; Trikalitis, P. N.; Kanatzidis, M. G. Z. Anorg. Allg. Chem. 2002, 628, 1568. (70) Lattumer, S. E.; Kanatzidis, M. G. Inorg Chem. 2004, 43, 2. (71) Wu, X. N.; Kanatzidis, M. G. J. Solid State Chem. 2005, 178. 3233. 16 (72) Chen, X. Z.; Larson, P.; Sportouch, S.; Brazis, P.; Mahanti, S. D.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 1999, 11, 75. (73) Zhuravleva, M. A.; Kanatzidis, M. G. Z. Naturforch B .' Sec. B 2003, 58, 649-657. (74) Chen, X. Z.; Small, P.; Sportouch, S.; Zhuravleva, M. ; Brazis, P.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 2000, 12, 2520. (75) Zhuravleva, M. A.; Pcionek, R. J .; Wang, X. P.; Schultz, A. J .; Kanatzidis, M. G. Inorg. Chem. 2003, 42, 6412. (76) Zhuravleva, M. A.; Evain, M.; Petricek, V.; Kanatzidis, M. G. J. Am. Chem. Soc 2007, 129, 3082. (77) Massalski, T, B. Binary Allory Phase Diagrams; 2nd ed.; ASM International: New York, 1990. (78) Canfield, P. C.; Fisk, Z. Z. Philos. Mag. B 1992, 65, l 1 17. (79) Bud'ko, S. 1.; Islam, Z.; Wiener, T. A.; Fisher, 1. R.; Lacerda, A. H.; Canfield, P. C. J. Magn. Magn. Mater. 1999, 205, 53. (80) Fisher, 1. R.; Islam, 2.; Canfield, P. C. J. Magn. Magn. Mater. 1999, 202, 1. (81) Hundley, M. F.; Sarrao, J. L.; Thompson, J. D.; Movshovich, R.; Jaime, M.; Petrovic, C.; Fisk, and Z. Phys. Rev. B 2001, 65, 024401. (82) Macaluso, R. T.; Sarrao, J. L.; Moreno, N. O.; Pagliuso, P.G.; Thompson, J. D.; Fronczek, F. R.; Hundley, M. F.; Malinowski, A.; Chan, J. Y. Chem. Mater. 2003, 15, 1394. (83) Sakarnoto, 1.; Shomi, Y.; Ohara, S. Physica B 2003, 329-333, 607. (84) Bailey, M. S.; McCuire, M. A.; DiSalvo, and F. J. J. Solid State Chem. 2005, 178, 3494. (85) Benbow, E. M.; Lattumer, S. E. Inorg. Chem. 2006, 179, 3989. 17 (86) Klunter, W.; Jung, W. J. Solid State Chem. 2006, 179, 2880. (87) Zaremba, V. 1.; Dubenskiy, V. P.; Rodewald, U. C.; Heying, B.; Pottgen, R. .1. Solid State Chem. 2006, 179, 891. (88) Lukachuk, M.; Galadzhun, Y. V.; Zaremba, R. 1.; Dzevenko, M. V.; Kalychak, Y. M.; Zaremba, V. I.; Rodewald, U. C.; Pottgen, R. J. Solid State Chem. 2005, 1 78, 2724. (89) Macaluso, R. T.; Sarrao, J. L.; Pagliuso, P.G.; Moreno, N. 0.; Goodrich, R. G.; Browne, D. A.; Fronczek, F. R.; Chan, J. Y. J. Solid Sate Chem. 2002, 166, 245. (90) Hegger, H.; Petrovic, C.; Moshopoulou, E. G.; Hundley, M. F.; Sarrao, J. L.; Fisk, Z.; Thompson, J. D. Phys. Rev. Lett. 2000, 84, 4986. (91) Moshopoulou, E. G.; Fisk, Z.; Sarrao, J. L.; Thompson, J. D. J. Solid State Chem. 2001, 158, 25. (92) Zaremba, V. 1.; Rodewald, U. Ch.; Hoffmann, R. —D.; Kalychak, Ya. M.; Pottgen, R. Z. Anorg. Allg. Chem. 2003, 629, 1157. (93) Zaremba, V. 1.; Rodewald, U. Ch.; Pottgen, R. Z Naturforsch. 2003, 58b, 805. (94) Pagliuso, P, G.; Sarrao, J. L.; Thompson, J. D.; Hundley, M. F.; Sercheli, M. S.; Urbano, R. R.; Rettori, C.; Fisk, Z.; Oseroff, S. B. Phys. Rev. B 2001, 63, 092406-1. (95) Salvador, J. R.; Bilc, D.; Gour, J. R; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2005, 44, 8670 (96) Salvador, J. R.; Gour, J. R.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2004, 43, 1403. (97) Salvador, J. R.; Hoang, K.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2007, 46, 6933 18 (98) Salvador, J. R. Molten metal flux synthesis and crystal growth of intermetallic silicides, germanides and indides.; Michigan State University: Dissertation, East Lansing, MI, 2004 (99) Salvador, J. R.; Kanatzidis, M. G. Inorg. Chem. 2006, 45. 7091. (100) Kalychak, Ya. M. J. Alloys Compd. 1997, 341, 262. (101) Szytula, A.; Leciejewicz, J. "Handbook of Crystal Structures and Magnetic Properties of Rare Earth Intermetallics"; CRC Press: Boca Raton, F1, 1994. (102) Maple, M. B. J. Phys. Soc. Jpn 2005, 74, 222. (103) Hossain, Z.; Gupta, L. C.; Geibel, C. J. Phys. : C ondens. Matter 2002, I4, 9687. (104) Gamza, M.; Slebarski, A; Rosner, H. J. Phys. .' Condens. Matter 2008, 20, 025201. (105) Lawrence, J. M.; Riseborough, P. S.; Park, R. D. Rep. Progr. Phys. 1981, 44, 1. (106) Lawrence, J .; Chen, Y.-Y.; Thompson, J. Theoretical and Experimental Aspects of Valence Fluctuations and Heavy F ermions; Plenum: New York and London, 1987. (107) Kindler, B.; Finsterbusch, D.; Graf, R.; Ritter, F.; Assmus, W.; Luthi, B. Phys. Rev. B 1994, 50, 704. (108) Stewart, G. R. Rev. Mod. Phys. 2006, 78, 743. (109) Wachter, P. Handbook on the Physics and Chemistry of Rare Earths 1994, (Elsevier Science, Amsterdam), 177. (110) Paglione, J.; Tanatar, M. A.; Hawthorn, D. G.; Boaknin, E.; Hill, R. W.; Ronning, F.; Sutherland, M.; Taillefer, L.; Petrovic, C.; Canfield, P. C. Phys. Rev. Lett. 2003, 91, 4. (111) Izawa, K.; Yamaguchi, H.; Matsuda, Y.; Shishido, H.; Settai, R.; Onuki, Y. Phys. Rev. Lett. 2001, 8705, 4. 19 (112) Fisk, Z.; Hess, D. W.; Pethick, C. J.; Pines, D.; Smith, J. L.; Thomson, J. D.; Willis, J. O. Science 1988, 239, 33. 20 CHAPTER 2 Mixed Valency in Yb7TM4InGe12 (TM = Co, Ni): 3 Novel Intermetallic Compound Stabilized in Liquid Indium 2-1. Introduction Molten metals can be excellent solvents for the synthesis of new intermetallic compounds.1 For example, molten A1 when used to investigate the reactivity of the quaternary systems RE/TM/Si(Ge) (RE = rare earth metal, TM = transition metal) readily gave rise to new complex quaternary phases such as szNi(Si|.,,Ni,,)A14Si62 REgRu12A1498i93 and REzNiAerez.4 In these cases a notable feature of this chemistry is the inclusion of A1 into the crystal structure. Interestingly, when Ga was employed in analogous reactions within the RE/TM/Si system, generally yielded Ga-free products (e.g. SmNiSi35) or Si-free products (e.g. szNi3S156 and szNiGa.;;_).7 When Si is replaced by Ge in the Ga flux reactions however, quaternary compounds such as RE3NI3G33GC38 and GdCot.,,Ga3Ge9 are readily observed. These are surprising differences in reactivity given the close relationship of A1 to Ga and Si to Ge respectively. These results imply that there is much new chemistry and reactivity to be learned by studying fluxes of related elements. Recently, we extended this work to include molten In as a solvent in the system RE/TM/Ge.'°’ ” Indium has been extensively used for the crystal growth of primarily known binary and ternary phases;I however, it has been less exploited as a synthetic flux medium compared to Al and Ga, especially for quaternary compounds.'2"6 Our work in In flux has led to very few quaternary phases such as the REaNizlnGea,I7 21 Among intermetallics that are likely to be stabilized in metallic fluxes, the Yb- containing ones are particularly attractive because they can display intriguing properties caused by the diverse character of their f electrons.l8 These electrons can play a dynamic role in bonding leading to intermediate valence, unusual magnetism, Kondo and heavy- fermion behavior, to name just a few.‘9 Yb can exhibit two valence states concerning the non-magnetic 4fM (Yb2+) and magnetic 4fl3 (Yb3+) electronic configurations. For this reason we investigated the reactivity of the Yb/Co/Ge system in liquid indium. Here, we present the ordered quaternary intermetallic compounds RE7C041nGe12 (RE = Dy, Ho and Yb) as well as the Ni analog YbyNialnGetz. This is another example besides REaNiglnGe4 where In is acting as a reactive flux in the RE/TM/Ge system. The Yb analogs are mixed valence compounds with predominant Yb3+ ions with Yb7C04InGe12 exhibiting negative magnetoresistance. 2-2. Experimental Section Reagents: The following reagents were used as purchased without further purification: Yb, Dy, H0 (in the form of powder ground from metal chunk, 99.9%, Chinese Rare Earth Information center, Inner Mongolia, China), Co (-325 mesh 99.9% Cerac Milwaukee WI), Ni (-325 mesh 99.9% Cerac Milwaukee WI), Ge (ground from 2-5 mm pieces 99.999% Plasmaterials Liverrnore, CA) and In (tear drops 99.99% Cerac Milwaukee, WI). 22 Synthesis: Method A: The RE7C041nGetz (RE = Dy, Ho, Yb,) and Yb7Ni4InGe12 compounds were obtained by combining 3 mmol of the corresponding rare earth metal, 2 mmol cobalt or nickel, 3 mmol germanium and 15 mmol In in an A1203 (alumina) crucible under an inert nitrogen atmosphere inside a glove-box. The crucible was placed in a 13 mm fused silica tube, which was flame sealed under vacuum of 10‘1 Torr, to prevent oxidation during heating. The reactants were then heated to 1000 0C over 10 h, maintained at that temperature for 4 h to allow proper homogenization, followed by cooling to 850 0C in 2 h and held there for 48 h. Finally, the system was allowed to slowly cool to 50 0C in 48 h. The reaction product was isolated from the unreacted In by heating at 350 0C and subsequent centrifugation through a coarse frit. The remaining flux was removed by immersion and soniqation in glacial acetic acid for 48 h. The final crystalline product was rinsed with water and dried with acetone. The yields of the reactions were 20-70% with purity ranging from 30% to 80% depending on the RE metal. Several crystals, which grow as metallic silver needles and tend to aggregate, were carefully selected for elemental analysis, structure characterization, differential thermal analysis, magnetic susceptibility, XPS, XANES and resistivity measurements. Method B: Yb7C04InGen was also prepared by combining 6 mmol ytterbium metal, 2 mmol cobalt, 5 mmol germanium and 15 mmol In in an A1203 (alumina) crucible under an inert nitrogen atmosphere inside a glove-box. The reactants were then heated under the same heating profile as in method A. This method increased the purity (90 %) and the yield (80 %) of the target phase. Attempts to generate the Yb7C041nGe12 phase by 23 direct combination of the elements in their stoichiometric ratios and heating in a RF induction heating furnace were not successful. YbyNialnGelz was initially prepared by combining 6 mmol ytterbium metal, 2 mmol cobalt, 5 mmol germanium and 15 mmol In in an A1203 (alumina) crucible under an inert nitrogen atmosphere inside a glove-box. The reactants were then heated under the same heating profile as in method A. It was later found that by mixing the reactants in the alternative ratio of 4:1 :4: 1 5 for Yb/Ni/Ge/In improved the yield in Yb7Ni4InGelz. Elemental Analysis: Semi-quantitative microprobe elemental analysis was performed on several crystals of the compound using a JEOL ISM-35C scanning electron microscope (SEM) equipped with a Noran Vantage Energy Dispersive Spectroscopy (EDS) detector. Data were acquired by applying a 25 kV accelerating voltage and an acquisition time of 40 s. A typical needle-like crystal of Yb7Co4InGe12 is shown in Figure 1. The EDS analysis taken on visibly clean surfaces of the Yb7C041nGe12 crystals gave the atomic composition of 31.5% Yb, 17.3% Co, 3.9% In and 48.4% Ge (ngCoaalnGetgs), which is in good agreement with the results derived from the single crystal X-ray diffraction refinement. Similar stoichiometric ratios were determined for the other RE analogs as well as the Ni one. 24 X-ray Crystallography: RE7Co4InGe12, The X-ray intensity data were collected at room temperature using a Bruker SMART Platform CCD diffractometer with graphite monochromatized Mo Ka (’1 = 0.71073 A) radiation. The SMART software was used for data acquisition and SAINT for data extraction and reduction.20 An empirical absorption correction was applied using the program SADABS20 and the structure of Yb7C041nGetz was solved by direct methods and refined with the SHELXTL package programs?! A stable refinement was accomplished only in the tetragonal space group P4/m. Standardization of the atomic positions of Yb7C04InGetz was performed with Platon-Structure Tidy application of the WinGX package software.22 Solutions of the Dy and Ho analogs were obtained by using the solution of Yb7CoalnGe12 as a starting point, with the final refinement done using SHELXTL. Interestingly, the Co and Ge(2) positions in the Dy and Ho analogs are switched compared to the Yb analog, and the Ge(3) atom is repositioned. This model gave a far better R values. For example, for the Dy and Ho analogs we obtain R1=0.025 8 and 0.0464 respectively. This compares to R1 = 0.0500 and sz = 0.0515 for the wrong model i.e. the one with the positions left unswitched (Yb-analog model). In addition, when these two sites are positioned as in the Yb analog the thermal displacement parameters become unreasonable. Data collection and structure refinement details are given in Table 2-1. The final atomic positions, equivalent isotropic displacement parameters and anisotropic displacement parameters are listed in Table 2-2 and 2-3. Yb7N14InGc12, The X-ray intensity data were collected at room temperature using a STOE IPDS 2T (with additional capability of 26 swing of the detector) diffractometer with graphite-monochromatized Mo K0101 = 0.71073 A) radiation. The X-AREA (and X- 25 RED and X-SHAPE within) package suite23 was used for data extraction and integration and to apply empirical and analytical absorption corrections. The structure of Yb7NialnGe12 single crystals were solved by direct methods and refined with the SHELXTL package programs.”‘ 24 A stable refinement was accomplished only in the tetragonal space group P4/m. Data collection and structure refinement details are given in Table 2-4. The final atomic positions, equivalent isotropic displacement parameters and anisotropic displacement parameters are listed in Table 2-5 and 2-6. 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Rambo 94v £w:2o>m>> OS 2:3quth E395 229—Hem £288 Row—imam 27 Table 2-2. Atomic coordinates (x 104) and equivalent isotropic displacement 3 parameters (A2 x 10 ) for RE7CoalnGe12 (RE = Dy, Ho, Yb). Atom Wyckoff x y z U(eq)a Dy(l) 4k 3232(1) 3259(1) 5000 7(1) Dy(2) 1a 0 0 0 8(1) Dy(3) 2f 0 5000 5000 8(1) Ge(l) 4j 2139(1) 5124(1) 0 7(1) Ge(2) 4j 1131(1) 2860(1) 0 10(1) Ge(3) 4k 1950(1) 655(1) 5000 11(1) Co 4j 2797(1) 1181(1) 0 7(1) In 1c 5000 5000 0 8(1) Ho(l) 4k 3245(1) 3260(1) 5000 8(1) Ho(2) la 0 0 0 8(1) Ho(3) 2f 0 5000 5000 10( 1) Ge(l) 4j 2139(2) 5102(2) 0 10(1) Ge(2) 4k 1 133(3) 2853(3) 0 18(1) Ge(3) 4j -664(3) 1957(3) 5000 17(1) Co 4j 2811(3) 1182(3) 0 9(1) In 1c 5000 5000 0 9(1) Yb(l) 4k 3262(1) 3243(1) 5000 5(1) Yb(2) 1a 0 0 0 5(1) Yb(3) 2f 0 5000 5000 7(1) Ge(l) 4j 2164(1) 4886(1) 0 5(1) Ge(2) 4j 2865(2) 1 130(1) 0 12(1) Ge(3) 4k 679(2) 1931(1) 5000 9(1) Co 4j 1191(2) 2800(2) 0 5(1) In 1c 5000 5000 0 7(1) aU(eq) is defined as one third of the trace of the orthogonalized Uij tensor. 28 Table 2-3. Anisotropic displacement parameters (A2 x 103) for RE7CoalnGze122(R%3 =HDy, Ho, Yb). Th?2 anisotropic displacement factor exponent takes the form: -21: [h a* U + +2hka*b*U ] Atom U11 U22 U33 U23 U13 U12 Dy(1) 7(1) 7(1) 8(1) 0 0 1(1) Dy(2) 7(1) 7(1) 8(1) 0 0 0 Dy(3) 7(1) 9(1) 8(1) 0 0 0(1) Ge(l) 8(1) 5(1) 9(1) 0 0 -1(1) Ge(2) 5(1) 6(1) 19(1) 0 0 0(1) Ge(3) 11(1) 15(1) 7(1) 0 0 -6(1) Co 6(1) 8(1) 7(1) 0 0 20) In 6(1) 6(1) 11(1) 0 0 0 Ho(l) 8(1) 8(1) 7(1) 0 0 2(1) Ho(2) 8(1) 8(1) 9(1) 0 0 0 Ho(3) 9(1) 11(1) 9(1) 0 0 -1(1) Ge(l) 10(1) 9(1) 10(1) 0 0 -1(1) Ge(2) 14(1) 14(1) 27(2) 0 0 3(1) Ge(3) 25(2) 17(1) 9(1) 0 0 11(1) Co 8(2) 9(2) 8(2) 0 0 80) In 8(1) 8(1) 12(2) 0 o 0 Yb(l) 3(1) 3(1) 10(1) 0 0 1(1) Yb(2) 3(1) 3(1) 10(1) 0 0 0 Yb(3) 4(1) 6(1) 11(1) 0 0 0(1) Ge(l) 4(1) 1(1) 11(1) 0 0 1(1) Ge(2) 5(1) 3(1) 26(1) 0 0 0(1) Ge(3) 12(1) 6(1) 10(1) 0 0 -6(1) Co 2(1) 3(1) 10(1) 0 0 -1(1) In 4(1) 4(1) 14(1) 0 0 0 29 Table 2-4. Crystal data and structure refinement data for Yb7Ni4InGetz. Emprirical formula Yb7Ni41nGe12 Formula weight 2432.02 Temperature (K) 293(2) Wavelength (A) 0.71073 Crystal system Tetragonal Space group P4/m a, b(A) 10.3091(15) c (A) 4.1691(8) Volume (A3) 443.08(12) Z / Density(calculated) (Mg/m3) 1 / 9.114 Absorption coefficient (mm'l) / F(000) 61.878 / 1035 6 range for data collection (°) 3.95 to 31.60 ~15 S h S 15 Index ranges ~15 S k S 15 -5 S 1 S 6 Reflections collected / unique 5126 / 834 R(int) 0.0503 Completeness to 6 (%) 99.3 Refinement method Full-matrix least-squares on F Z Data / restraints / parameters 834 / 0 / 4O Goodness-of-fit on FL 1.394 Final R indices [I>20(I)] (R1 / wR2)a 0.0276 / 0.0538 R indices (all data) (Rl /wR2)a 0.0294 / 0.0544 Largest diff. peak and hole (e. A'3) 1.996 and -1 .725 / 1,. an =2141tall/41:. ; we =[zwlcl-1FJr/alct] 142141. 30 Table 2-5. Atomic coordinates (x 104 ) and equivalent isotropic displacement parameters (A2 x 103 )for Yb7NialnGetz. Atom ' gifts? y z U(eq)a Yb(l) 4k 6751(1) 3275(1) 5000 6(1) Yb(2) la 10000 0 0 6(1) Yb(3) 2f 5000 0 5000 7( 1) Ge(l) 4j 7812(1) 5111(1) 0 6(1) Ge(2) 4j 8863(1) 2879(1) 0 10(1) Ge(3) 4k 10674(l) 1915(1) ~5000 12(1) Ni 4j 8810(2) 2794(2) 0 6(1) In 1c 5000 5000 0 7(1) aU(eq) is defined as one third of the trace of the orthogonalized Uil tensor. Table 2-6. Anisotropic displacement parameters (A2 x 103 ) for Yb7Ni41nG§n2 (RE= Dy, Ho, Yb). Th5:2 anisotropic displacement factor exponent takes the form: ~21: [h a* 2U + ... +2hka*b*U ] Atom U11 U22 U33 U23 U13 U12 Yb(l) 6(1) 6(1) 6(1) 0 0 —1(1) Yb(2) 5(1) 5(1) 7(1) 0 0 0 Yb(3) 9(1) 6(1) 7(1) 0 0 0(1) Ge(l) 6(1) 4(1) 7(1) 0 0 0(1) Ge(2) 4(1) 6(1) 19(1) 0 0 0(1) Ge(3) 21(1) 11(1) 5(1) 0 0 40(1) Ni 6(1) 7(1) 6(1) 0 0 2(1) In 7(1) 7(1) 9(1) 0 0 0 31 Differential Thermal Analysis: Differential Thermal Analysis (DGA) was conducted with a Shimadzu TDA-SO analyzer. The sample was flame sealed under a reduced atmosphere in fused silica ampoules that were carbon coated to prevent glass attack upon melting of the products. 01- Ale3 standard was used as a reference. The analysis was performed by heating the sample up to 1000 0C at a rate of 10 OC per min, held at 1000 0C for 1 min then cooling to 100 0C at the same rate, and then repeating the cycle. Magnetic Measurements: Magnetic susceptibility measurements for REyCoalnGetz (RE = Yb and Dy) were carried out with a Quantum Design MPMS SQUID magnetometer. EDS-analyzed crystals were soaked in ~ 6M of HCl acid for 15-30 min, washed out with water, and dried out in a dry oven. The crystals were then randomly placed and sealed in Kapton tape which was inserted into the SQUID magnetometer. Temperature dependent data were collected between 3 and 400 K, with an applied field of 500 G. Field dependent magnetic measurements were acquired at 3 K with field sweeping from ~ 50000 to 50000 G. X-Ray Photoemission Spectroscopy: X-ray Photoemission Spectroscopy was performed on a Perkin Elmer Phi 5400 ESCA system equipped with a Magnesium K01 X-ray source. Samples were analyzed at pressures between 10'9 and 10'8 torr with a pass energy of 29.35 eV and a take-off angle 32 of 45°. The spot size was roughly 250 umz. All peaks were referenced to the signature C 1 5 peak for adventitious carbon at 284.6 eV. X-ray Absorption Near Edge Spectroscopy (XAN ES): X-ray absorption fine Structure (XAFS) experiments were performed in Sector 20, bending magnet beamline (PNC/XOR, 20-BM) of the Advanced Photon Source at the Argonne National Laboratory, IL, USA. Measurements at the Yb Lin-edge for Yb7TM41nGe12 (TM = Co, Ni) were performed in the transmission mode using gas ionization chambers to monitor the incident and transmitted X-ray intensities. A third ionization chamber was used in conjunction with a copper foil to provide internal calibration for the alignment of the edge positions. Monochromatic X-rays was obtained using a Si (111) double crystal monochromator. The monochromator was calibrated by defining the inflection point (first derivative maxima) of Cu foil as 8980.5 eV. A Rh- coated x-ray mirror was utilized to suppress higher order harmonics. The Yb sample was prepared as a pellet from fine grounded amounts of around 1.8 mg and 180 mg of hexagonal BN. Measurements were performed at a range of temperatures from 15 K to 300 K using a closed cycle refrigerator. XAFS samples were prepared by mixing an appropriate amount of the finely ground Yb compound with BN. The mixture was pressed to form a self-supporting pellet, which was mounted on the cold finger of a closed-cycle refiigerator. Care was taken to suppress distortion in the data from thickness effects. 33 Magneto-Transport Measurements: Magneto-transport measurements were performed on a needle-shaped crystal of Yb7C041nGe12 with approximate dimensions of 648 x 56 x 75 um and the long direction oriented parallel to the crystallographic c-axis. Four gold wires were attached with silver paint, and the resistance of the sample was obtained in a standard four-probe measurement with a current of 100 11A. By averaging the sample voltage corresponding to positive and negative currents we eliminated artifacts due to the thermal voltages. The sample was inserted into a superconducting magnet equipped with a variable temperature insert that allows controlling of the sample’s temperature between 1.2 K and 320 K. The magnetic field was oriented perpendicular to the needle. 2-3. Results and Discussion Reaction Chemistry: Yb7Co4InGe12 was first observed from indium flux as silvery thin needles frequently aggregated in bundles. Figure 2-1(A) and (B) shows scanning electron micrographs of typical Yb7Co4InGeiz and Dy7Co4InGe12 crystals, respectively. Other reaction products for the Yb analog included szlnGe2,25‘ 26 Yb5CoaGeto,27 the cubic phase YbIn3 and recrystallized germanium. Subsequent tuning of the reaction conditions increased the yield and eliminated all byproducts except szlnGez which, due to its very different crystal morphology, was easily distinguishable. When other RE metals such as La, Ce, Sm, Eu, Dy, Ho and Er were employed under the same reaction conditions only Dy and Ho were able to form the same phase but in much smaller yield. This suggests that the size of the rare-earth cations likely plays a decisive role for the formation of 34 RE7C041nGe12. The reaction targeting the Dy7CoalnGe12 member of the present compounds also produced the quaternary phase DyaCoInGea, which will be discussed in the following chapter. The Yb7CoalnGe12 compound does not melt up to 1000 0C; as confirmed by differential thermal analysis. Yb7NialnGe12 grows similarly as silvery thin needles often aggregated in bundles. From the reactions designed to produce the Ni quaternary compound a ternary compound was also observed, in which In was excluded from the product, as resulted from EDS analysis on many crystals. Subsequent single crystal X-ray diffraction analysis on those crystals gave the new ternary Yb2N11_5G€2_5 (or YbaNi3Ge5) phase which will be described in a future work. It should be noted at this point, that when Yb was employed as the RE in the reactions targeted to form the Yb analog of the REaNiglnGea familyl7 Yb7NialnGe12 was produced instead. This reinforces the suggestion stated above, that the size of the rare-earth cations probably plays a crucial role for the formation of these compounds. 5011111 5011111 (A) (3) Figure 2-1. Scanning Electron micrograph (SEM) images of flux-grown crystals of (A) YD7CO4IIIG612 and (B) Dy7CoalnGe12. 35 Structure: The RE7Co4InGe12 (RE = Dy, Ho, Yb) compounds and Yb7Ni4InGelz crystallize in the tetragonal P4/m space group with the Ca7Ni4Sn13 structure type.28 RE7TM41nGetz is an ordered quaternary variant of this ternary phase, with the RE atoms occupying the Ca positions, the Co/Ni atoms the Ni sites and the Ge atoms adopting the Sn positions. The fact that the quaternary compound orders in this way is consistent with the more electropositive nature of the RE (compared to Co/Ni, In and Ge) and that they are more likely to adopt the electropositive Ca site within the compound. Additionally, it is expected for the transition metals of Co/Ni to adopt the Ni position, and as Ge is in the same group as Sn, it is not surprising that Ge atoms order on the Sn sites. Because of their isostructural nature we will describe the structure in terms of the Yb7Co4InGe12 analog. The overall structure of Yb7Co4InGe12 as viewed down the c-axis is depicted in Figure 2-2. The bonds to the Yb atoms were omitted to emphasize the three-dimensional (3D) [CoalnGeiz] framework and its channels. This network is characterized by three different types of channels, propagating along the c-axis, in which the Yb atoms are situated. Another way to look at the [CoalnGetz] SUb-structure is in terms of columns of octagonal and hexagonal rings that run along the a and b-axes, while the void space between them is filled up by four pentagons related by the 4-fold axis of the tetragonal symmetry. The polygonal rings are connected down the c-axis via Co-Ge(3)-Co zigzag chains. The biggest channels in the structure are built up from stacked alternating planar layers of distorted octagons and square planes, Figure 2-3. The octagons are comprised 36 from alternating Co(l) and Ge(2) atoms while the Yb(2) atoms are sitting in their center. The two Co(1)—Ge(2) interatomic distances at 2.390(2) and 2.434(2) A, fall in the Co-Ge bond range found in other binary or ternary intermetallicszg‘ 30 Similar octagonal channels can be found in YbsTaGeto27 and in general in the RE5TM4X10 series” 32 (RE = rare earth, Sc or Y, TM = C0, Rh, Ir or Os and X = Si, Ge or Sn) which they all adopt the tetragonal ScsCo4Siio (P4/mbm) structure”. Another structural feature is the hexagonal tunnels, Figure 2-3. In these, two Ge(1)~Ge(2) dimers are interconnected with two Co atoms to form distorted hexagonal rings which are stacked parallel to the c-axis and are connected via Ge(3) atoms. In contrast to the octagonal tunnels, here, the Yb(3) atoms are sandwiched between the hexagons. The Ge(1)~Ge(2) interatomic distances at 2.548(2) A, are comparable with Ge- Ge contacts observed in many RE germanides with 2D and 3D networks including the IioSthGem29 at 2.539 A. The final noteworthy structural moiety is the pentagonal channels which are fused in groups of four that share a central column of square planar In atoms, see Figure 2-2. A Ge(l)-Ge(2) dimer is linked to a C0 and an In atom from the Ge(2) and Ge(l) site, correspondingly; both of them connect to another Ge(l) atom, thus forming pentagonal rings that extend along the c-axis through one Co-Ge(3)~Co zigzag chain (Figure 2-3). The Co-Ge(2) and Co-Ge(1) distances at 2.434(2) A and 2.369(2) A, respectively, are also found in the two other types of rings. The four-coordinated In atoms are bonded to four Ge(l) atoms (with In-Ge(1) bond at 2.9214(14) A) in a square-planar environment. This is a rare coordination environment for a group 13 element. A similar In coordination environment was also found in REzlnGe2.25‘ 26 In the pentagonal channels, as in the case 37 of the hexagonal ones, the Yb(l) atoms are located between the pentagonal layers. There are no direct Co-Co bonds in the structure. An alternative way to view the Yb7CoalnGe12 structure is in polyhedral representation. Figure 2-4(A) depicts the connectivity of the Co-centered Ge tetragonal pyramids as viewed down the c-axis. Four such polyhedra share their Ge(2) comers in the a,b-plane, forming square rings, see Figure 2—4(B). These squares stack along the c-axis by connecting trough the Ge(3) corners of the pyramids to form square tubes that extend down the c-axis, Figure 2-4(C). These tubes are aligned parallel to each other, and every such tube is connected directly to four other neighboring tubes through Ge(l)-Ge(2) bonds at 2.548(2) A to build the 3D [Co4InGe12] framework. The Yb(2) atoms reside within the tubes, whereas Yb(l) and Yb(3) atoms are located between adjacent square tunnels. The local coordination environments (within 3.5 A) of the RE atoms are illustrated in Figure 2-5. RE(l) atoms are 11-coordinate and are sitting in the center of a pentagonal prism, made up of six Ge(l), two Co and two In atoms, and are capped with one Ge(3) atom. The RE(2) atoms have 16 neighbors in their immediate coordination sphere. These include four Ge(2) and four Co atoms in a form of a flat octagonal ring (where the RE(2) is the center) and eight additional Ge(3) atoms with four located above and four below the octagon in a square prismatic geometry. Finally, RE(3) exhibit a coordination number of fourteen, in an arrangement that is best described as a hexagonal prism comprising four Ge(l), four Ge(2) and four Co atoms, capped by two Ge(3) atoms. Tables 2-7 and 2-8 give a complete list of the bond distances for REyCoalnGeiz and Yb7Ni41nGe12, correspondingly. 38 Figure 2-2. The overall structure of Yb7C041nGe12 as viewed onto the a, b-plane. For clarity the bonds to the Yb atoms are not drawn. 39 Figure 2-3. The octagonal, hexagonal and pentagonal rings and their interconnection to form the corresponding tunnels running down the c-axis. 40 Figure 2-4. (A) Polyhedral view of the Yb7C041nGetz structure featuring the connectivity between Co-centered Ge tetragonal pyramids. (B) The polyhedra share Ge(2) comers to form squares. (C) Stacking of squares along the c-axis forming square tubes. 41 Ge1 Figure 2-5. The coordination environment of the RE atoms. The coordination sphere cutoff is 3.4 A. 42 Table 2-7. Bond lengths [A] for RE7Co4InGetz (RE = Dy, Ho, Yb)_ Bond RE=Dy RE=Ho RE=Yb RE(1)-Ge(l) 2.9336(9) 2.932(1) 2.9060(10) RE(1)-Ge(3) 3.0048(13) 3.001(3) 2.9820(16) RE(1)-Co 3.0329(11) 3.025(2) 3.0102(13) RE(1)-Ge(l) 3.0610(9) 3.043(2) 3.0298(10) RE(1)-Ge(2) 3.0441(9) 3.045(2) 3.0340(1 1) RE(1)-In 3.3109(4) 3.2965(11) 3.2838(5) RE(1)~RE(1) 3.6324(8) 3.6204(18) 3.5983(8) RE(2)-Ge(3) 2.9829(9) 2.983(2) 2.9575(10) RE(2)-Co 3.1428(14) 3.158(3) 3.1323(17) RE(3)-Ge(1) 3.0473(9) 3.039(2) 3.0473(10) RE(3)-Ge(3) 3. 2300(12) 3. 226(3) 3.2360(15) RE(3)-Ge(2) 3.2620(9) 3.262(2) 3.2392(12) RE(3)-Co 3.3257(11) 3.309(3) 3.3074(14) Ge(1)-Co 2.3702(18) 2.378(4) 2.369(2) Ge( 1 )-Ge(2) 2.5652(17) 2.552(4) 2.548(2) Ge(l)-In 2.9643(12) 2.965(3) 2.9214(14) Ge(2)-Co 2.3937(19) 2.398(4) 2.390(2) Ge(2)-Co 2.4493(19) 2.453(4) 2.434(2) Ge(3)-Co 2.3302(9) 2.3203(19) 2.3213(10) 43 Table 2-8. Selected Bond lengths [A] for Yb7NialnGelz. Bond Length Yb(1)~Ge( 1) 2.9086(7) Yb(1)~Ge(1) 3.0208(7) Yb(1)-Ge(3) 3.0139(11) Yb(1)-Ge(2) 3.0419(8) Yb(1)-Ni 3.0316(9) Yb(1)~In 3.2809(5) Yb(l)~Yb(1) 3.5831(7) Yb(2)-Ge(3) 2.9539(8) Yb(2)-Ni 3.1290(1 l) Yb(3)-Ge(l) 3.0732(7) Yb(3)-Ge(2) 3.2405(8) Yb(3)-Ge(3) 3.2553(11) Yb(3)-Ni 3.3209(9) Ge(l)-Ni 2.3938(14) Ge(2)-Ni 2.43 83(1 5) Ge(2)-Ni 2.4002(1 5) Ge(3)-Ni 2.3336(7) Ge(1)-Ge(2) 2.5430(13) Ge(1)-In 2.9016(10) 44 Magnetic Measurements: Magnetic susceptibility data for Yb7C041nGetz are presented in Figure 2-6(A). The temperature dependence of the molar susceptibility (Xm) displays paramagnetic behavior suggesting the existence of Yb3+ moments in the material. No magnetic ordering was observed down to 3.5 K. The inverse susceptibility does not follow the Curie-Weiss law especially at the temperature region below 100 K, which can be attributed to crystal- field contributions and / or to a possible onset of a valence fluctuation. The weak linearity of the data precluded the unequivocal determination of the pen: However, analyzing the susceptibility data in a proper temperature range (T > 100 K) with the modified Curie- Weiss law 1(7) = )(o + C / (T — 6,,) yields information concerning the sum of the temperature-independent conributions )(0, e. g. van Vleck paramagnetism, paramagnetism due to conduction electrons, and core-electron diamagnetism, the effective magnetic moment peer (deduced from the Curie constant C), and the Weiss constant 6p. A nonlinear least-squares fit to this equation resulted in yo = 1.9 x 10'3 emu/mol Yb, 6,, = ~38 K indicating antiferromagnetic interactions among the Yb atoms, and an effective moment of 3.1 [13 / Yb, which is ~68% of the value expected for the free-ion Yb“, 4.54 [13. This means that more than half of the Yb atoms are in the Yb3+ state. This is supported by the XANES studies presented below. The field dependence of magnetization for Yb7Co4InGe12 at 3 K can be found in Figure 2-6(B). The magnetization increases linearly up to a field of 20 kG, at which point the slope continuously changes until approximately 33 kG where it becomes linear again, but with a much shallower slope. The response remains linear up to the highest attainable field with no signs of saturation up to 50 kG. The moment reaches a value of only 2.7 pg 45 per formula which is about 30 % of the value anticipated for the fully saturated moment of seven Yb3+ ions.. 0.5 r . 1 35 30 0.4 A 8 425 z E 03 .. 3x \ - .20 g =3 9. 5 0.2 “ 15 (T E a x ~10 5 0.1 -5 AAA k 0 l I 1 I 1 L l 0 0 50 100 150 200 250 300 350 400 Temperature (K) a (B) o 2 - E \ 3°“ ' a x g) 2 A. E ' ‘9‘ ‘9 r J l l l l -410“ -210‘ o 2104 410‘ Field (G) Figure 2-6. (A) Temperature dependence of the molar susceptibility xm (triangles) and inverse l / xm (circles) for YbyCoalnGeiz with an applied field of 500 G. (B) Magnetization data for Yb7Co4InGe12 collected at 3 K. 46 Temperature dependent magnetic susceptibility x(M/H) data performed on randomly oriented single crystals of DyyCoalnGeiz are plotted in Figure 2-7(A). Due to the very small size of the sample we were not able to determine the weight and as result we could not calculate the molar susceptibility. Nevertheless, the compound seems to undergo a ferromagnetic transition that onsets at a Tc of ~ 21 K as indicated by a change in the slope of x. As it can be clearly seen from the inset in Figure 2-7(A), the ZFC (zero field cooled) and FC (field cooled) data reveal considerable different behavior at the low temperature range starting at ~ 8 K. The ferromagnetic order of the spins is also confirmed from the field dependent magnetic moment data measured at 3 K, given in Figure 2-7(B). Apparent hysteresis loops appear up to at least 20 k6 and — 20 kG, while the moment does not seem to saturate up to the highest attainable field of 50 kG. 47 _, (A) 2.510 ‘ A ’5‘ 7 a 2.510‘7 . ”‘3‘... o ‘ 210'7 . A A. V ‘ A 6‘1510'7 ‘ 1.510”: “ ‘ 4 ‘ A g T 110'7 g -1 V 1 10‘7 1- 2 _8 .1 x 510 ‘ ‘ ‘ A A Al 510‘°_}‘\0 8 111 2'4 32 40 .- ‘48 AAA A AAAAAA A A A AAAAAAAA A O I I L I I I I o 50 100 150 200 250 300 350 400 Temperature (K) -3 / 1.510 - (B) j l,./ 1 1 10‘3 - '- /N. 3 -4 , E 510 - ,7 - d) ,/ V r 0 1‘5 E 0 10 - I.“ I: -1 a g -510" - - -1 10'3 b ‘ -3 .4 ’1 ~‘l.5 10 - /-- . -4104 -210‘ 0 210‘ 410‘ Field (G) Figure 2-7. (A) Temperature variation of the susceptibility x(M/H) for Dy7Co4InGe.2 with an applied field of 500 G. Inset shows the low temperature (0-40 K) data. (B) Magnetic moment data for Dy7Co4InGetz collected at 3 K. 48 XPS Measurements: To further probe the Yb oxidation state in Yb7Co4InGelz we performed X-ray photoelectron spectroscopy (XPS) measurements. The XPS spectrum revealed a strong peak at ~ 185 eV and a multiplet structure at higher energies (Figure 2-8). This type of spectrum is consistent with the presence of Yb3+ ions.“ 35 With careful inspection of the spectra, we see two very weak peaks at ~18] and 191 eV. This double peak is known from the literature that is attributed to Yb2+ ions.34 80 . N 75 . . 2 >< #5 70 - d :3 5’; 3 65 - . s: 8 1+ U i so - - 9 55 l l l I l 175 180 185 190 195 200 205 Binding Energy (eV) Figure 2-8. XPS spectra of Yb 4d core level for Yb7Co4InGe12 at 300 K. 49 XANES Measurements: Because XPS is a surface analytical technique it was crucial to carry out X-ray absorption near-edge spectroscopy (XANES) measurements at the Yb Lin-edge, which is an established method for studying the valence of the absorbing element. XANES ftmdamentally probes the bulk of the sample. The near-edge spectra of an Yb4Co7InGe12 sample obtained at 15 K and 300 K are given in Figure 2-9. The main absorption peak (white line) for both spectra is centered at ~ 8948 eV, which is typical of trivalent Yb, both in oxide form as well as in Yb intermetallics.”38 Relative to Yb“, divalent Yb exhibits a white line which is ~ 8 eV lower in energy.”38 The spectra also reveal the presence of a weaker feature (shoulder) at ~ 8940 eV, indicating that some divalent Yb is also present. Another interesting observation in the XANES spectra is that the relative ratio of the features at 8940 and 8948 eV varies weakly with temperature. In particular, with increasing temperature the low-energy peak originating from Yb2+ ion is slightly depressed, whereas the high-energy one originating from Yb3+ ion is enhanced, suggesting that the average valence of Yb is slightly temperature dependent and that the Yb3+ state is more populated at higher temperatures. Similar behavior was observed in the YbCu5.,,Gax series}9 Figure 2-10 displays both the spectra of the present phase and Yb203 at room temperature. To ensure that we are not observing spectra from oxide impurities, we also computed and compared the XAFS of Yb4Co7InGe12 with that of Yb203 standard. The absence of Yb-O bonds shows that the Yb in the sample is not coordinated to oxygen, indicating that the trivalent character is intrinsic to Yb4C07InGe12, Figure 2-11. 50 An attempt to obtain the relative amount of Yb3+ and Yb2+ was performed by representing the normalized Yb XANES as a pair of pseudo-Voigt and modified arc- tangent functions. We estimate the amount of Yb3+ to be ~ 73% with an error of ~ 15%. A more accurate determination of Yb valence will require measurements of Yb2+ and Yb3+ standards (or analogs) with similar structure to the sample under study and will be a subject of future investigations. 2 j I I I "Yb 300K / \ Yb 15K ’ \\ 6 1.5 h \ ' 3 \ c6 2+ / 3+ \ v \ C \\ .2 1 - / T "\n. 1 E.“ .-:/ O ,/ (I) 7. < 0.5 - / - ,/ // 0 PT ““““ l 1 1 8930 8940 8950 8960 Figure 2-9. Lm absorption edge spectra of Yb in Yb7Co4InGe|2 at 15 K (dashed line) and 300 K (solid line). Energy (eV) 51 3 l I r j I I t —Yb 300K 2.5 '- 00. .I. - ,7 ----- Yb 0 300K ;' '- 5 2 3 ' I s; 2 ' s ‘ a: ;' ' .3 1.5 E‘ O U) _Q 1 <2 0.5 o 8930 8940 8950 8960 Energy (eV) Figure 2-10. Comparison of Yb7Co4InGe12 (solid line) and Yb203 (dashed line) spectra at room temperature. 1.6 . . . . 1.4 _ :'~:.<—Yb-O . a 5= .52 1'2 b 3: -—Yb Co InGe 15K ' g ,‘g 7 4 l2 on 1 - : : ----- Yb 0 RT - g : : 3 3 <2 :' ': m I I. g . H t— Figure 2-11. The Fourier Transform (FT) of the Yb XAFS for Yb4C07InGe12 (15 K) compared with that for szO3 (RT). The FT’S are not corrected for photo-electron phase shifts. The k-range of the FT was 3-10 A". 52 X-ray absorption near-edge spectroscopy (XANES) measurements at the Yb L1”- edge were also performed for the Yb4Ni7InGe12 compound. The near-edge spectra of an Yb4Ni71nGe12 sample obtained at 18 K and 295 K are given in Figure 2-12. The double- peaked structure of the spectra for both measured temperatures indicates that the Ni compound is also a mixed-valence compound. Additionally, the relative ratio of the features at 8940 and 8948 eV, originating from Yb2+ and Yb3+ ions respectively, varies weakly with temperature. Particularly the Yb3+ state tends to be more populated at higher temperatures, as it was also observed for the Yb4C07InGe|2 compound. An attempt to estimate the relative amount of Yb3+ and Yb2+ resulted in a Yb3+ content of ~ 73 (5) %. I I I I I I I ',.‘_ Yb18K l {Ci\ 1 16 -——-—Yb295K . I ./ 3 + ..L N l L Absorption (a. u.) O on 0.4 - / - // v'1’r// 1 I l l 1 I 8930 8940 8950 8960 Energy (eV) Figure 2-12. Lm absorption edge spectra of Yb in Yb7Ni4InGelz at 18 K (dashed line) and 295 K (solid line). 53 Magneto-Transport Measurements: The temperature dependence of the resistivity (p) for samples of Yb4Co7InGen with and without the application of magnetic field is shown in Figure 2-12. The resistivity data measured on single crystals along the c-axis and at zero applied field reveal a rather moderate metallic behavior with p ~ 205 ,uQ cm at 246 K. The inset in Figure 2-13 displays the low-temperature ,0 data at a field of 0. 1 and 5 T applied perpendicular to the c-axis. It can be clearly seen that the material displays negative- magnetoresistance at low temperatures (i.e. the resistivity drops with increasing applied field). This behavior is frequently seen in many Kondo or Heavy Fermion systems and it is attributed to the suppression of scattering of the conduction electrons from the unpaired f-electrons in a high field. 200 ' J S x 150 §1oo IE . . . ‘5': - 96‘: - .5 h I g 50 - 92 1 : 88 5 . 84: i i O -- I L I L n n I 810 n 5“ i 1.0 I .15. I. L29 m L @- 40 80 120 160 200 240 Temperature (K) Figure 2-13. Variable temperature single-crystal resistivity data for Yb7C04InGe|2 at zero field. Inset: displays the low temperature resistivity data at 0, 1 and 5 T field. 54 Both magnetic susceptibility and XANES measurements suggest that the Yb4Co7InGe12 is a new heterogeneous mixed-valence compound, i.e., a system with both Yb3+ and Yb2+ sites with about two thirds of the Yb atoms being in the Yb3+ (P3) state. Because there are three crystallographically distinct Yb sites, we can possibly speculate that two of them have atoms in the Yb3+ configuration and one in the Yb2+ configuration. To assign which site could possibly accommodate Yb2+ ions, we can compare the coordination environment of each Yb site. The nearest neighbor distances for Yb(l) are 2.9060 (Yb-Ge) and 3.0102 (Yb-Co) A, respectively, whereas those for the Yb(2) site are 2.9575 (Yb-Ge) and 3.1323 (Yb-Co) A, respectively. The corresponding distances for the Yb(3) site are 3.0473 (Yb-Ge) and 3.3074 (Yb-Co) A, respectively. Because the distances around the Yb(3) sites are considerably longer than those of the other two sites, a plausible conclusion is that the Yb2+ ions with their larger ionic radius probably occupy the Yb(3) site. 2-4. Conclusions Four new quaternary RE7TM41nGe12 phases crystallize in molten In in the tetragonal P4/m space group with the CayNi4Sn13 structure type. The flux seems necessary to stabilize these compounds because direct combination of the elements and induction heating reactions with various stoichiometric ratios failed so far to form them. In general, when studying systems of the type RE/M/Ge in liquid In, the tendency is for In not to get incorporated into the compound. In the case of REyTM4InGe12, we observe the reactive nature of the flux where In enters the structure of the final product. The fact that only Dy, Ho and Yb form the RE7Co4InGe12 and only Yb the corresponding Ni 55 compound (other RE atoms produced the RE4Ni21nGe4 phase), suggests that the size of the rare-earth cations likely plays a decisive role for the formation of these compounds. The Yb7Co4InGe12 and Yb7Ni4InGe12 are mixed valence compounds with a high Yb3+/Yb2+ ratio which is slightly temperature dependent. Because of the small yields of the other two RE analogs complete property characterization could not be performed. Nevertheless, preliminary magnetic susceptibility measurements for Dy7C04InGe12 indicate ferromagnetic ordering below 21 K. 56 References: l. Kanatzidis, M. G.; Péittgen, R.; Jeitschko, W., Angewandte Chemie-International Edition 2005, 44, (43), 6996-7023. 2. Chen, X. Z.; Sportouch, S.; Sieve, B.; Brazis, P.; Kannewurf, C. R.; Cowen, J. A.; Patschke, R.; Kanatzidis, M. G., Chemistry of Materials 1998, 10, (10), 3202-3211. 3. Sieve, B.; Chen, X. Z.; Henning, R.; Brazis, P.; Kannewurf, C. R.; Cowen, J. A.; Schultz, A. J.; Kanatzidis, M. G., Journal of the American Chemical Society 2001, 123, (29), 7040-7047. 4. Sieve, B.; Trikalitis, P. N.; Kanatzidis, M. G., Zeitschrift Fur Anorganische Und Allgemeine Chemie 2002, 628, (7), 1568-1574. 5. Chen, X. Z.; Larson, P.; Sportouch, S.; Brazis, P.; Mahanti, S. D.; Kannewurf, C. R.; Kanatzidis, M. G., Chemistry of Materials 1999, ll, (1), 75-83. 6. Zhuravleva, M. A.; Kanatzidis, M. G., Zeitschrift Fur Naturforschung Section B-a Journal of Chemical Sciences 2003, 58, (7), 649-657. 7. Chen, X. 2.; Small, P.; Sportouch, S.; Zhuravleva, M.; Brazis, P.; Kannewurf, C. R.; Kanatzidis, M. G., Chemistry of Materials 2000, 12, (9), 2520-2522. 8. Zhuravleva, M. A.; Pcionek, R. J .; Wang, X. P.; Schultz, A. J .; Kanatzidis, M. G., Inorganic Chemistry 2003, 42, (20), 6412-6424. 9. Zhuravleva, M. A.; Evain, M.; Petricek, V.; Kanatzidis, M. G., Journal of the American Chemical Society 2007, 129, (11), 3082-3083. 10. Salvador, J. R.; Bilc, D.; Gour, J. R.; Mahanti, S. D.; Kanatzidis, M. G., Inorganic Chemistry 2005, 44, (24), 8670-8679. 11. Salvador, J. R.; Gour, J. R.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G., Inorganic Chemistry 2004, 43, (4), 1403-1410. 12. Bailey, M. S.; McGuire, M. A.; DiSalvo, F. J ., Journal of Solid State Chemistry 2005, 178, (11), 3494-3499. 57 l3. Benbow, E. M.; Lattumer, S. 13., Journal of Solid State Chemistry 2006, 179, (12), 3989-3996. 14. Klunter, W.; Jung, W., Journal of Solid State Chemistry 2006, 179, (9), 2880- 2888. 15. Lukachuk, M.; Galadzhun, Y. V.; Zaremba, R. 1.; Dzevenko, M. V.; Kalychak, Y. M.; Zaremba, V. 1.; Rodewald, U. C.; Pottgen, R., Journal of Solid State Chemistry 2005, 178, (9), 2724-2733. 16. Zaremba, V. 1.; Dubenskiy, V. P.; Rodewald, U. C.; Heying, B.; Pottgen, R., Journal of Solid State Chemistry 2006, 179, (3), 891-897. 17. Salvador, J. R.; Kanatzidis, M. G., Inorganic Chemistry 2006, 45, (18), 7091- 7099. 18. Lawrence, J. M.; Riseborough, P. S.; Parks, R. D., Reports on Progress in Physics 1981, 44, (1), 1-84. 19. Kindler, B.; Finsterbusch, D.; Graf, R.; Ritter, F.; Assmus, W.; Luthi, 8., Physical Review B 1994, 50, (2), 704-707. 20. Sheldrick, G. M. SADABS and SAINT, version 4; University of Gottingen: Gottingen, Germany, 1995. 21. Sheldrick, G. M. SHELXT L, Structure Determination Program, version 5; Siemens Analytical X-ray Instruments Inc.: Madison, WI, 1995. 22. Farrugia, L. J. WinGX, Solution, Refinement and Analysis of Single Crystal X-Ray Diffraction Data, version 1.70.01; University of Glasgow: Glasgow, Scotland, 1997- 2005. . 23. GmbH, S. C., 2006, D 64295 Darmstadt, Germany. 24. Bruker, Advanced X—ray Solutions SHELXT L (Version 6.14), Bruker AXS Inc., Madison, WI (2003). 58 25. Zaremba, V. 1.; Tyvanchuk, Y. B.; Stepien-Damm, J., Zeitschrift Fur Kristallographie-New Crystal Structures 1997, 212, (2), 291-291. 26. Tobash, P. H.; Lins, D.; Bobev, S.; Lima, A.; Hundley, M. F.; Thompson, J. D.; Sarrao, J. L., Chemistry of Materials 2005, 17, (22), 5567-5573. 27. Katoh, K.; Tsutsumi, T.; Yamada, K.; Terui, G.; Niide, Y.; Ochiai, A., Physica B- Condensed Matter 2006, 373, (1), 111-119. 28. Vennos, D. A.; Badding, M. E.; Disalvo, F. J., Journal of the Less-Common Metals 1991, 175, (2), 339-346. 29. Mruz, O. Y.; Belsky, V. K.; Gorelenko, Y. K.; Skolozdra, R. V.; Bodak, O. I., Ukrainskii F izicheskii Zhurnal 1987, 32, (12), 1856-1858. 30. Welter, R.; Venturini, G.; Malaman, B.; Ressouche, B, Journal of Alloys and Compounds 1993, 201, 191-196. 31. Patil, N. G.; Ramakrishnan, 8., Physical Review B 1999, 59, (14), 9581-9589. 32. Becker, B.; Patil, N. G.; Ramakrishnan, S.; Menovsky, A. A.; Nieuwenhuys, G. J .; Mydosh, J. A., Physical Review B 1999, 59, (1 1), 7266-7269. 33. Braun, H. F.; Yvon, K.; Braun, R. M., Acta Crystallographica Section B- Structural Science 1980, 36, (OCT), 2397—2399. 34. Chung, J. S.; Cho, E. J.; Oh, S. J., Physical Review B 1990, 41, (9), 5524-5528. 35. Szytula, A.; Jezierski, A.; Penc, B.; Winiarski, A.; Leithe-Jasper, A.; Kaczorowski, D., Journal of Alloys and Compounds 2003, 360, (1-2), 41-46. 36. Rao, C. N. R.; Sarma, D. D.; Sarode, P. R.; Sampathkumaran, E. V.; Gupta, L. C.; Vijayaraghavan, R., Chemical Physics Letters 1980, 76, (3), 413-415. 37. Hatwar, T. K.; Nayak, R. M.; Padalia, B. D.; Ghatikar, M. N.; Sampathkumaran, E. V.; Gupta, L. C.; Vijayaraghavan, R., Solid State Communications 1980, 34, (8), 617- 620. 59 38. Moreschini, L.; Dallera, C.; Joyce, J. J.; Sarrao, J. L.; Bauer, E. D.; Fritsch, V.; Bobev, S.; Carpene, E.; Huotari, S.; Vanko, G.; Monaco, G.; Lacovig, P.; Panaccione, G.; Fondacaro, A.; Paolicelli, G.; Torelli, P.; Grioni, M., Physical Review B 2007, 75, (3), 035113. 39. Bauer, E.; Tuan, L.; Hauser, R.; Gratz, E.; Holubar, T.; Hilscher, G.; Michor, H.; Perthold, W.; Godart, C.; Alleno, E.; Hiebl, K., Physical Review B 1995, 52, (6), 4327- 4335. 60 CHAPTER 3 Flux Synthesis of the New Quaternary Intermetallic Dy4CoInGe4 Exhibiting Complex Magnetic Behavior 3-1. Introduction The ternary systems of RE/TM/In and RE/TM/Ge (RE = rare earth metal and TM = transition metal) have been the subject of intensive investigations in the last few decades. These studies resulted in numerous novel intermetallic compounds with a variety of different crystal structuresl and interesting magnetic and electrical properties.2 Of the large number of intermetallic compounds in these systems, specifically the examination of those containing Co as the transition metal yield many phases with rich structural diversity and composition. Kalychack has made a concentrated effort to generalize and present the crystallographic characteristics of the RE/Co/In systems containing compounds with established crystal structure.3 Additionally, both RE/Co indides and germanides have attracted much interest because they exhibit a variety of intriguing electrical and physical phenomena, which include heavy fermions, superconductivity and their coexistence, pressure induced superconductivity, Kondo lattices, magnetic ordering, mixed-valent and valence fluctuating behavior to name a few.4'“ Notable cobalt-containing indides include the heavy fermion superconductor at ambient pressure CeCoIns with transition temperature T, of 2.3 K, the discovery of which sparked an intense and continuous research of the CeTMIns (TM = C0, Ir, Rh) family of compounds.“'6 It was later shown in more detailed studies that CeCoIns is an 61 unconventional superconductor very close to a quantum phase transition (QPT) at ambient pressure with d—wave symmetry below Tc = 2.2 K7’l2 while a magnetic quantum critical point (QCP) can be achieved by the application of a magnetic field of the order of the upper critical field Hc2(0).l3 In the REzCoIng systems the Ce analog is a Kondo lattice, exhibiting also heavy fermion superconductivity at ambient pressure with T, = 0.4 K,8‘9 while the Dy and Ho ones display field induced ferromagnetic behavior at low temperatures.9 On the other hand, noteworthy germanides comprise the CeCoGez which is a heavy fermion Kondo compound with T K > 200 K"), while the non-stochiometric CeCoo_ggGe2 exhibits heavy-fermion and valence fluctuating behavior.ll Interestingly, the stoichiometric CeCoGe absorbs very slowly hydrogen at 393K under a pressure P(H2) = 2MPa.” Recently, it has been demonstrated that molten metal fluxes, particularly Al and Ga, are excellent preparative tools for the exploratory synthesis of intermetallic compounds.15 Our own work in the systems RE/TM/Al/Si or Ge established that Al acts exclusively as a reactive flux producing complex quaternary phases. In contrast Ga flux, which readily leads to quaternary phases in the systems RE/TM/Ga/Ge, has a considerably reduced tendency to form quaternary compounds in the corresponding RE/TM/Ga/ Si systems. “'28 Lately, we extended this work to include molten In as a solvent in the system RE/TM/Ge.”33 Indium flux, although it has been commonly used in the past for the 1534'” it has been less crystal grth of primarily known binary and ternary phases exploited as a synthetic tool for the discovery of new compounds compared to Al and Ga, particularly for quaternary phases, despite the most recent efforts.”43 Our work in the 62 exploratory synthesis of RE/TM/In/Ge indicates that, as in the case of Ga/Si system, it is difficult to readily produce quaternary phases and includes a limited number of quaternary phases so far. These are the RE4Ni;;_InGe43 l and RE7Co41nGe12.3'3 The discovery of the RE/Co/In or Ge phases and their remarkable properties justifies the interest in the exploratory. synthesis of the type RE/Co/In/Ge. Here we present the novel quaternary compound Dy4CoInGe4, grown from In flux which crystallizes as a new structure type. The synthesis and the study of the crystal structure and magnetic properties are reported. Dy4ColnGe4 seems to exhibit ferromagnetic behavior below 40 K. 3-2. Experimental Section Reagents: The following reagents were used as purchased without further purification: Dy, (in the form of powder ground from metal chunk, 99.9% Chinese Rare Earth Information center, Inner Mongolia, China), Co (-325 mesh 99.9% Cerac Milwaukee WI), Ge (ground from 2-5 mm pieces 99.999% Plasmaterials Liverrnore, CA) and In (tear drops 99.99% Plasmaterials Liverrnore, CA). Synthesis: The Dy4CoInGe4 compound was first obtained by combining 3 mmol of the dysprosium metal, 2 mmol cobalt, 3 mmol germanium and 15 mmol In in an A1203 (alumina) crucible under an inert nitrogen atmosphere inside a glove-box. The crucible was placed in a 13 mm fused silica tube, which was flame sealed under vacuum of 104 63 Torr, to prevent oxidation during heating. The reactants were then heated to 1000 0C over 10 h, maintained at that temperature for 5 h to allow proper homogenization, followed by cooling to 850 0C in 2 h and held there for 48 h. Finally, the system was allowed to slowly cool down to 50 0C in 48 h. The reaction product was isolated from the excess In flux by heating at 350 0C and subsequent centrifugation through a coarse frit. Any remaining flux was removed by immersion and soniqation in glacial acetic acid for 48-72 h. The final crystalline product was rinsed with water and dried with acetone. Several crystals, which grow as metallic silver needles / rods were carefully selected for elemental analysis, structure characterization, and the physical measurements reported here. Impurity byproducts were the quaternary Dy7Co4InGe12 (see Chapter 2) and small amounts of DyzlnGez and Dyi.2Ge (or DyGe). Dy4CoInGe4 was also prepared by combining the Dy/Co/Ge/In reagents in 612:5:20 and 2:1:1:5 mmol at later attempts to modify the synthesis. The remaining reaction profile was the same as described above. These reactions decreased the amount of the formed byproducts and resulted in ~ 50 — 65 % yield of the target phase of Dy4CoInGe4. Elemental Analysis: Semi-quantitative microprobe elemental analysis was performed on several crystals of the compound using a JEOL JSM-35C scanning electron microscope (SEM) equipped with a Noran Vantage Energy Dispersive Spectroscopy (EDS) detector. Data were acquired by applying a 25 kV accelerating voltage and an acquisition time of 40 s. A typical needle-like crystal of Dy4CoInGe4 is shown in Figure 1. The EDS analysis taken on visibly clean surfaces of the Dy4CoInGe4 crystals gave the atomic composition 64 of 39.98-42 % Dy, 8.83-10.90 % Co, 8.85-1 1.98 % In and 38.96-40.45 % Ge, which is in very good agreement with the results derived from the single crystal X-ray diffraction refinement. X-ray Crystallography: The X-ray intensity data were collected at room temperature using a Bruker SMART Platform CCD diffractometer with graphite monochromatized Mo Ka (I. = 0.71073 A) radiation. The SMART software was used for data acquisition and SAINT for data extraction and reduction. An empirical absorption correction was applied using the program SADABS and the structure of Dy4CoInGe4 was solved by direct methods and refined with the SHELXTL package programs. A stable refinement was accomplished only in the monoclinic space group C12/m1. In the structure of Dy4CoInGe4 all atomic sites were refined anisotropically. Data collection and structure refinement details are given in Table 3-1. The final atomic positions, equivalent isotropic displacement parameters and anisotropic displacement parameters are listed in Table 3-2 and 3-3. 65 Table 3-1. Crystal data and structure refinement data for DyaCoInGea. Empirical formula DyaCoInGea Formula weight 4456.44 Temperature (K) 293(2) Wavelength (A) 0.71073 Crystal system Monoclinic Space group C12/m1 a (A) 20.080(8), a= 90° b (A) 4.1963(17), B: 104.637(6)° c (A) 10.192(4), y = 90° Volume (A3) 830.9(6) Z / Density(calculated) (Mg/m3) l / 8.906 Absorption coefficient (mm-l) 54.285 F (000) 1872 Theta range for data collection 2.07 to 28.240 Index ranges ~24Sh525 / -5$k55 / 4231313 Reflections collected / unique 4618 / 1099 R(int) 0.0517 Completeness to 6 (%) 93.7 Refinement method Data / restraints / parameters Goodness-of—fit on F2 Final R indices [1>2o(1)] (R1 /wR2)a R indices (all data) (R1 / wR2)a Extinction coefficient Largest diff. peak and hole (e. A'3) Full-matrix least squares on F 2 1099 / 0 / 64 1.111 0.0301/ 0.0640 0.0379/ 0.0688 0.00116(6) 1.890 and -2.897 1,, aRl zillFol'tiil/ZIFOI;WR2 =|:Zw{]F0l-ch|}2/ZM1F0|2]" 2iw21/0'21F0ll' 66 4 Table 3-2. Atomic coordinates (x 10 ) and equivalent isotropic displacement parameters 2 3 (A x 10 )for Dy4ColnGe4. Atom 33.8.8? y z Uteq)“ Dy(1) 4i 2777(1) 0 6479(1) 7(1) Dy(2) 4i 3693(1) 0 3580(1) 6(1) Dy(3) 4i 3687(1) 0 10076(1) 5(1) Dy(4) 4i 4600(1) 0 7300(1) 6(1) In(l) 2a 5000 -5000 10000 10(1) In(2) 2c 5000 -5000 5000 10(1) Ge(l) 4i 2013(1) 0 8567(2) 6(1) Ge(2) 4i 4340(1) 50% 2172(2) 6(1) Ge(3) 4i 3652(1) -5000 81 10(2) 6(1) Ge(4) 4i 1375(1) 0 4449(2) 10(1) C0 4i 2598(1) 50% 8934(2) 7(1) 0LU(eq) is defined as one third of the trace of the orthogonalized Uil tensor. 67 Table 3-3. Anisotropic displacement parameters (A2 x 103) for DyaCoInGea. Atom U11 U22 U33 U23 U13 U12 Dy(1) 5(1) 8(1) 6(1) 0 0(1) 0 Dy(2) 6(1) 6(1) 5(1) 0 2(1) 0 Dy(3) 6(1) 6(1) 5(1) 0 2(1) 0 Dy(4) 5(1) 7(1) 6(1) 0 1(1) 0 111(1) 7(1) 15(1) 7(1) 0 2(1) 0 In(2) 9(1) 13(1) 6(1) 0 0(1) 0 Ge(l) 7(1) 6(1) 6(1) 0 2(1) 0 Ge(2) 6(1) 6(1) 6(1) 0 0(1) 0 Ge(3) 7(1) 7(1) 5(1) 0 1(1) 0 Ge(4) 18(1) 7(1) 5(1) 0 4(1) 0 C0 6(1) 7(1) 9(1) 0 2(1) 0 2 2 2 11 The anisotropic displacement factor exponent takes the form: -21t [h a* U +... + 2hk a* 12 b"‘ U ] Magnetic Measurements: Magnetic susceptibility measurements were carried out with a Quantum Design MPMS SQUID magnetometer. EDS-analyzed crystals were soaked in ~ 6M of HCl acid for 15-30 min, washed out with water, and dried out in a dry oven. The crystals were then randomly placed and sealed in Kapton tape envelope which was inserted into the SQUID magnetometer. Temperature dependence data were collected between 3 and 400 K, with an applied field of 100, 500 and 1000 G. Field dependent magnetic measurements were acquired at 3, 18 and 60 K with field sweeping from - 50000 to 50000 G. 68 3-3. Results and Discussion Reaction Chemistry: The compound DyaCoInGea was first discovered in a reaction that was initially designed to form Dy7C041nGe12, a phase that can only be synthesized from In flux,33 see Chapter 2. The reaction produced single and clustered crystals in the form of metallic silver needles and rods. The rod shaped crystals were first mistakenly identified as Dy7CoalnGelz, but were later determined to be DyaCoInGea after elemental analysis and subsequent single crystal diffraction experiments were performed. Modifications of ratios of the initial reagents improved the yield of the targeted DyaCoInGea phase however small amounts of the Dy7C041nGelz phase were still formed as well. Other impurity byproducts were small amounts of DyzlnGez and Dy12Ge (or DyGe) which due to their different crystal morphology of cubic and square pyramid respectively, they were easily removed. Attempts to synthesize DyaColnGea by direct combination reactions failed to produce the targeted phase. Figure 3-1 shows a scanning electron micrograph of a typical rod type Dy4CoInGe4 crystal. 69 r if 1070 pm Figure 3-1. Scanning Electron micrograph (SEM) image of a flux-grown DyaColnGea rod—shaped crystal. Structure: DyaCoInGea crystallizes in the monoclinic C12/m1 space group in what appears to be a new structure type. The overall structure of the compound as viewed down the b-axis is depicted in Figure 3-2. The bonds to the Dy atoms were omitted in order to emphasize the three dimensional [CoInGe4] framework and its channels. The [CoInGea] sub-lattice is characterized by l2-membered and 5-membered channels propagating along the b-axis in which the Dy atoms are situated and CozGe(1)2 ribbons. Figure 3-3 shows the principal building unit the repetition of which makes up the whole [CoInGea] network. It consists of pentagonal channels which are fused in groups of four that share a central column of square planar In( 1) atoms. These channels consist of two different types of pentagonal rings. In one of them a Ge(3)-Ge(4) dimer is linked 70 to In(1) from the Ge(3) and to In(2) (also in square planar geometry) atom from the Ge(4) site correspondingly and both In atoms connect to a C0 atom. Both of these pentagonal rings in the group of four, share their In(2) atom with similar pentagons of other fused groups that are on the same level, thus propagating the main building block along the c- axis, see Figure 3-2. The other type of pentagons consists of a Ge(l)-Ge(2) dimer which connects to a C0 and an In(1) atom from the Ge(2) and Ge(l) side respectively, while a Ge(3) atom bonds to both Co and In(1) to form the second type of ring. The Co-Ge(l) side of these pentagons connects with two Co-Ge(1) bonds to the corresponding side of similar pentagons extending the structure along the a-axis, but which are found on a lower level down the b-axis, as it can be seen in the Figure 3-4 (structure view in a,b- plane with RE atoms removed to emphasize the connectivity). Dy(3) and Dy(4) are found in the center of the pentagonal channels. Similar group of four fused pentagonal channels sharing a square planar In atom is also found in the REyCoalnGen33 intermetallic compounds presented in Chapter 2 as well as in the family of the ternary phase REzlnGez.44 The two Ge-Ge distances of 2.630(2) and 2.595(2) A compare well with the Ge dimmers observed in other RE germanides such as the ,B-RENiGe229 compounds with Ge-Ge bonds ranging from 2.423(4) to 2.821(4) A. The other part of the repeating unit the CozGe(l)2 rhombi (Figure 3-3), are fused and form double zigzag chains (or ribbons) that run down the monoclinic b-axis as shown in Figure 3-4. These ribbons connect the pentagonal rings along the b-axis, thus forming the corresponding channels and building the 3D [CoInGe4] framework. The Ge(l) atoms are in a trigonal pyramidal geometry composed of two Co and one Ge(2) atom and the Co atoms are surrounded by three Ge(l) and one Ge(3) atom forming a tetrahedral 71 coordination. Ge atoms in a trigonal pryrarnidal coordination enviromnent forming ribbons with transition metals is found also in other intermetallic compounds as in REaNizlnGea31 and several RExCoylnz3 phases, for example. The Co-Ge(1) bond that forms the zigzag double chains is at 2.3875(13) A and is shorter than the Co-Ge(l) bond which fuses the chains together into a ribbon with a length of 2.468(3). The void space left from the repetition of the main building unit, forms the highly corrugated 12-membered channels, as seen in Figure 3-5, in which the Dy(1) and Dy(2) atoms are residing. The Ge(2) and Ge(3) atoms are both in a trigonal planar bonding arrangement while the Ge(4) are in a bent geometry. There are no direct C0-C0 bonds in the structure similar to RE7C041nGe12, As mentioned above, the group of four fused pentagonal channels that share a central column of square planar In atoms is also found in the tetragonal RE7C041nGe1233 intermetallic compounds. Additionally, the CozGe(l)2 ribbons resemble the NizGe(1)2 ribbons found in the monoclinic RE4Ni21nGe43' compounds. This suggests that the DyaCoInGea structure is some kind of an “intermediate” between these two compounds. Figure 3-6 displays the structures of the a,c-view of DyaColnGea (P4/m, a = 10.3522(5), c = 4.1784(5)) and Dy4Ni21nGe4 (C2/m, a = 15.420(2), b = 4.2224(7), c = 7.0191(ll)) and the a,b-view of Dy7C041nGetz for comparison. The fused groups of the pentagonal channels and the ribbons are highlighted. The local coordination environments (within 4 A) of the four crystallographically distinct Dy atoms are illustrated in Figure 3-7. Dy(1) atom is 8-coordinate, forming bonds with three Ge(4) atoms, two Ge(3) atoms, one Ge(l) atom and two Co atoms, in a way that could be described as capped “boat-like” arrangement. The Dy(1)-Ge bond distances 72 range from 2.9198(17) to 3.0023(14) A while the two Dy(1)-Co bonds are at 3.3533(18) A. The Dy(2) atom exhibits a coordination number of eight and sits in the center of a distorted tetragonal prism, made up of twolGe(1), two Ge(2), two Ge(4) and two In(2) atoms. The Dy(2)-Ge bonds vary from 2.9311(14) up to 3.1033(14) A while the Dy(2)- In(2) distance is at 3.3865(10) A. The Dy(3) atom is surrounded by 12 atoms which form a bicapped pentagonal prism. The prism is composed of two Ge(l), two Ge(2), two Ge(3) and two In(1) atoms and is capped by a C0 and Ge(l) atom. For Dy(3) the nearest Ge atom in the pentagonal rings of the prism is at 2.8895(14) A while the furthest one creates a bond at 3.0462(13) A. The Dy(3)-In(1) and Dy(3)-Co bonds are equal to 3.3850(11) and 3.0419(16) A, correspondingly. The capping Ge(l) and Co atoms are at a distance of 3.3248(19) and 3.000(2) A, respectively. Finally, the Dy(4) atom has 10 neighbors in its immediate coordination sphere forming a pentagonal prismatic geometry with Dy(4) as the center and it is comprised of two Ge(2), Ge(3), Ge(4), In(1) and In(2) atoms. The shortest Dy(4)-Ge bond is at 2.9405(13) A and the longest one at 3.1059(14) A. The In(1) and In(2) atoms are found at 3.3912(11) and 3.3909(10) A away from the RE atom correspondingly. 73 #:5th “0: Be 888 n> one 9 mwcon 2: .3920 Lo..— .mwxmé ofi :Boc 3363 we SDEoUiQ MO 83023 2825 of. .Ntm 0.53% . hug x? a); o._ .. . . \Vt’unvfig)=:’. ... .. .. . .x. -.1... . . 00° . {infirm-xx 0.1.”: .. 74 Figure 3-3. The principal building unit the repetition of which makes up the whole [CoInGe4] network. Figure 3-4. Projection of the [CoInGe4] network roughly onto the a,b-plane. The RE atoms were removed to emphasize the connectivity. 75 Figure 3-5. Twelve-membered rings and their interconnection to form the corrugated channels. The RE atoms were removed to emphasize the connectivity. 76 30:12.5 ,3 53-9.3 2: Q as 305.8 demtmanQ 8m BEfiwG Pa mouaosbm SD mo 303-93 05 Am: 6050va0 mo 263-96 05 mo 2058.85 A361". Baum...— 77 Figure 3-7. Coordination environment of the Dy(1), Dy(2), Dy(3) and Dy(4) atoms. The coordination sphere cutoff is 4.0 A. 78 lit . An alternative view of the Dy4CoInGe4 structure is in polyhedral representation. Figure 3-8 displays the structure of the title compound as Co-centered tetrahedra and In(1),In(2)-centered planar squares as viewed in the a,c-plane. Similar square planes stack along the b-axis while alternating In(1) and In(2) squares connect through a Ge(3)- Ge(4) bond and by comer-sharing of their Ge(2) site and form chains that run along the c- axis. The Dy(4) atoms are found in the trigonal channels formed within these chains. The In(1)-centered square planes also connect through Ge(1)-Ge(2) bonds and by comer- sharing of their Ge(3) sites with the Co-centered tetrahedra along the a-axis. Dy(3) atoms are siting within the trigonal channels formed between the squares and the tetrahedra. Finally, the Co tetrahedra form fused zigzag columns down the b-axis by two Ge(1)-Ge(1) edge-sharing thus building the three dimensional [CoInGe4] framework, Figure 3-9. Dy(1) and Dy(2) atoms reside within the big channels created by the void space between the chains of the In squares and the fused columns made from the Co tetrahedra. Table 3-4 gives a list of selected bond distances for Dy4CoInGe4. 79 05365 2: E 3263 mm 8353 Sam—Q BSEQQANVEAGE was «6052:: 85:50-00 05 do 33:82:00 2: wccamfl 832:3 6050920 2: mo cocficomoae Emmi—om .w m 2:»?— 80 Figure 3-9. Stacking of the Co-centered tetrahedra and In(1)-centered planar squares along the b-axis. The tetrahedral are fused, forming zigzag columns that extend down the b-axis. 81 Table 3-4. Selected bond lengths [A] for Dy4CoInGe4. Bond Length Bond Length Dy(1)-Ge(1) 2.9198(17) Dy(3)-Ge(l) 3.0462(13) Dy(1)-Ge(3) 2.9622(13) Dy(3)-Ge(l) 3.3248(19) Dy(1)-Ge(4) 3.0023(14) Dy(3)-In(1) 3.3850(11) Dy(1)-Ge(4) 3.0429(19) Dy(4)-Ge(2) 2.9405(13) Dy(1)-Co 3.3533(18) Dy(4)-Ge(3) 3.0823(13) Dy(1)-Dy(4) 3.5427(17) Dy(4)-Ge(4) 3.1059(14) Dy(1)-Dy(2) 3.6081(13) Dy(4)-In(2) 3.3909(10) Dy(l)- Dy(1) 3.6099(15) Dy(4)-In(1) 3.3912(11) Dy(2)-Ge(4) 2.931 1(14) In(1)-Ge(2) 2.8530(17) Dy(2)-Ge(2) 3.0159(13) In(1)-Ge(3) 2.8995(17) Dy(2)-Ge(1) 3.1033(14) In(2)-Ge(2) 2.8517(18) Dy(2)-Co 3.151(2) In(2)-Ge(4) 2.9531(19) Dy(2)-In(2) 3.3865(10) Ge(1)-Co 2.3875(13) Dy(2)-Dy(3) 3.5692(17) Ge(l)-Co 2.468(3) Dy(3)-Ge(3) 2.8895(14) Ge(1)-Ge(2) 2.630(2) Dy(3)-Co 3.0419(16) Ge(3)-Co 2.465(2) Dy(3)-Co 3.000(2) Ge(3)-Ge(4) 2.595(2) Dy(3)-Ge(2) 3.0446(14) 82 Magnetic Measurements: Temperature dependent molar magnetic susceptibility, XmU) and inverse susceptibility, l/xm(T) data performed on randomly oriented single crystals of Dy4CoInGe4 are plotted in Figure 3-10. At a first glance, Dy4CoInGe4 seems to undergo a rather broad ferromagnetic transition that onsets at a To of ~ 20 - 25 K as indicated by a change in the slope of xm. As it can been clearly seen from the inset in Figure 3-10, the ZF C (zero field cooled) and FC (field cooled) data reveal considerable different behavior at the low temperature range starting slightly from ~ 40 K while separating completely at ~ 18 K. A closer look in the ZFC data reveals a maximum of the susceptibility at T1 = 8.5 K suggesting a change in the magnetic structure. Similar multitransitional magnetic behavior has been seen in spin structures with frustrated moments as in the RNiAl intermetallic compounds.45 The small cusp at ~ 60 K is probably due to some oxygen trapped in the sample. Above 60 K, the l/Xm data follow the Curie-Weiss law with a resulting effective magnetic moment of 14.1 113 per formula unit, and a Weiss constant of 0 = — 17.5 K. The observed effective magnetic moment is quite lower than the theoretical value of 21.3 1.13 for four free Dy3+ ions. This difference might be ascribed to strong crystal-field effects46 and also due to diamagnetic signal of the holder. The spins of the Dy3+ ions are consequently the only species contributing to the magnetic moment. The negative Weiss constant indicates antifferomagnetic interactions between the RE atoms. In order to study the observed transitions in further detail we performed temperature dependent molar magnetic susceptibility Xm(T) measurements on randomly oriented single crystals of Dy4CoInGe4 at three different applied fields of 100, 500 and 1000 G, see Figure 3-11. Below a ferromagnetic transition at TC = 40 K the Xm(T) curve 83 remarkably varies depending on the ZFC and the FC conditions for all three applied fields, whereas increase of the field from 100 G to 1000 G tends to suppress the divergences between the ZFC and FC curves. In Figure 3-12 the Xm(T) data for the temperature range 0 — 100 K are given for all three fields. In the data collected at 100 G a sharp cusp appears in the ZFC curve at Tf‘ = 40 K and irreversibility, appearing as the evident separation between the ZFC and FC curves, starts at the temperature TS = 50 K. With increasing the magnetic field, T s shifts towards lower temperatures, particularly it shifts to 40 K and 30 K for the fields of 500 G and 1000 G, respectively. Furthermore, the peak in the erc curve loses intensity and broadens with increasing field. Additionally, more cusps appear in the lower temperature region for all curves that could mean further changes in the magnetic structure (possibly antiferromagnetic interactions). These features are characteristic to spin systems with frustrated moments and magnetic anisotropy that could lead to spin—glasses transitions.45‘47'5O In order to characterize the cusp temperature as spin-freezing transitions, further study with additional techniques is required. It should be noted here, that although in both measurements care was taken in order to place the single crystals randomly in the kapton tape folder that does not preclude the possibility of having a slightly preferred orientation of the crystals. This could create subtle differences between various measurements. Finally, the field dependent magnetization data taken at the temperatures of 3, 18 and 60 K are displayed in Figures 3-13. The material shows metamagnetic behavior. The magnetization measured at 3 K displays roughly linear response up 12 RG with a small remnant magnetization at zero field, whereas it exhibits pronounced hysteresis loops at higher fields for both positive and negative fields, which indicates ferromagnetic ordering 84 of the spins. The moment does not saturate up to the highest attainable field and reaches a value of about 5.5 ,uB which is only ~ 28 % of the value expected for 4 Dy3+ ions, calculated from unmade) = g] = 10 113 The metamagnetic behavior can be seen also in the curve measured at 18 K, inset in Figure 3-13. The dependence of magnetization on field is roughly linear up to 25000 G, where a spin reorientation begins to occur suggesting a more ferromagnetic arrangement of the moments while at about 35000 G a small hysteresis loop in formed. On the other hand the magnetization measured at 60 K shows linear dependence with the field indicating that Dy4CoInGe4 is paramagnetic at this temperature. Many other intermetallic compounds have shown complex spin behavior such as the quaternary phases DyzAuAl6Si425 and DyAuAl4Ge228 and the ternary B- DyNiGe229 to name just a few. The magnetic properties of the rare-earth containing intermetallic compounds have been the subject of intensive research. It is generally believed that the collective behavior of the magnetic rare-earth ions in these compounds is determined by an indirect interaction among localized f electrons which are coupled through the mediation of the conduction electrons according to the Ruderman-Kittel-Kasuya-Yosida (RKKY) theory.5 "53 85 1 I I I I 20 0.8 -15 Q r—t o \ E 0.6 a: \ a E -10 a 3 \ XE 0.4 l g i 5 L5 0.2 o o Figure 3-10. Temperature dependence of the molar susceptibility xm(T) and inverse susceptibility l/Xm(T) of randomly oriented single crystals for Dy4CoInGe4 collected with an applied field of 500 G. Inset shows the low temperature data of the susceptibility Xm(T)- 86 I I I I r I ‘ xm(100G) - xm ( 500(1) A . (“(10000) - '6' E . 3 E 3.; - RE 4% T 05 - its . I ‘1 D H I I Q I‘ E B I 8 D B I U I D S 8 F 0 50 100 150 200 250 300 350 400 Temperature (K) Figure 3-11. Temperature dependence of the molar susceptibility Xm(T) of Dy4CoInGe4 on single crystals randomly oriented with applied fields of 100 G, 500 G and 1000 G. 87 3.2 q "‘ 5. FC ‘ IOOG 2.8 h “ xm( ) . 2.4 ’ 1 2 ' A 7 1.6 " A 50 K . 12 '- ‘AA A ‘ Al -1 xZFC ‘ T : A A 0.8- 40K ‘AUH d 3 I. I. It I. b viii?» ‘12,; FC _ . 2.5 l- xm (DOUG) - '5 E 2 QUE 40 K 7 \ :85 "~'-'..r.;z'r.<:"-: ~ ~ 1 3 1.5 - ZFC . trf .- E X 1 - 1 0.5 : f '1 : i 2.5 :"g. FC .. . O O. xm(1000G)l O 30 K 2 O - \ . l ZFC ...: 1.5 " ° - 0 O 0 1 ' . . 1 O O . . o o l 0.5 L l I J 0 20 40 60 80 100 Temperature (K) Figure 3-12. Low temperature (0 - 100 K) variation of pm of Dy4CoInGe4 at applied fields of 100, 500 and 1000 G in order to emphasize the magnetic transitions. 88 B Magnetization (u / mol) -6 - o . 1 - . 4 - o 210‘I 410‘ I I L I L 4104 -2104 o 2104 4104 Field(G) Figure 3—13. Magnetization curves of Dy4CoInGe4 collected at 3 K (solid line) 18 K (dotted line) and 60 K (dashed line). Inset shows the magnetization curve at 18 K in the positive fields area. The arrow indicates the metamagnetic transition. 89 3-4. Conclusions Single-crystals of the new quaternary compound Dy4CoInGe4 were grown using an excess of indium as a flux. The flux seems necessary to stabilize this compound, since direct combination reactions failed to produce the new phase. Dy4CoInGe4 forms in the monoclinic space group C12/ml as a new structure type. The synthesis of Dy4CoInGe4 is the third example of In acting as a reactive flux in the system RE/TM/Ge. This is an interesting result because, as it was stated above it is difficult to isolate quaternary phases in this system, in contrast with analogous reactions when Al or Ga are used as molten metal fluxes. The discovery of Dy4CoInGe4 which is closely related to the structure and synthetic conditions of the RE7Co4InGe12 and RE4Ni21nGe4 compounds that were also stabilized in In flux, illustrates the remarkable ability of In flux, to produce novel complex intermetallics, when coupled with the right synthetic conditions. Magnetic susceptibility measurements of the material revealed a ferromagnetic transition with a Tc z 40 K with a complex picture below To that suggests the Dy4CoInGe4 could be a system with spin frustrated moments and behavior similar to spin-glasses. The magnetization measurements below and above Tc temperatures showed metamagnetic behavior and support the complex spin behavior observed in the susceptibility data. The small size of the crystals prevented the thorough investigation of its physical and electrical properties. Future work with this system should include attempts to produce bigger size crystals in order to further characterize the new material, with techniques such as ac-susceptibility, neutron diffraction and transport properties. 90 References: (1) Kalychak, Ya. M. J. Less-Common. Metals 1997, 262-263, 341. (2) Szytula, A.; Leciejewicz, J. "Handbook of Crystal Structures and Magnetic Properties of Rare Earth Intermetallics"; CRC Press: Boca Raton, F1, 1994. (3) Kalychak, Y. M. J. Alloy. Compd. 1999, 291, 80-88. (4) Hegger, H.; Petrovic, C.; Moschopoulou, E. G.; Hundley, M. F .; Sarrao, J. L.; Fisk, 2.; Thompson, J. D. Phys. Rev. Lett. 2000, 84, 4986. (5) Petrovic, C.; Movshovich, R.; Jaime, M.; Pagliuso, P. G.; Hundley, M. F.; Sarrao, J. L.; Fisk, 2.; Thompson, J. D. Europhys. Lett. 2001, 53, 354-359. (6) Petrovic, C.; Pagliuso, P. G.; Hundley, M. F .; Movshovich, R.; Sarrao, J. L.; Thompson, J. D.; Fisk, Z.; Monthoux, P. J. Phys. -Condes. Matter 2001, 13, L337-L342. (7) Izawa, K.; Yamaguchi, H.; Matsuda, Y.; Shishido, H.; Settai, R.; Onuki, Y. Phys. Rev. Lett. 2001, 8 705, 4. (8) Chen, G. F.; Ohara, S.; Hedo, M.; Uwatoko, Y.; Saito, K.; Sorai. M.; Sakamoto, 1. Journal of the Physical Society of Japan 2002, 71, 2836-2838. (9) Joshi, D. A.; Tomy, C. V.; Malik, S. K. J. Phys.-Condes. Matter 2007, I9, 0953- 8984. (10) Mun, E. D.; Lee, B. K.; Kwon, Y. S.; Jung, M. H. Phys. Rev. B 2004, 69, 5. (11) Pecharsky, V. K.; Gschneidner, K. A. Phys. Rev. B 1991, 43, 8238-8244. (12) Movshovich, R.; Jaime, M.; Thompson, J. D.; Petrovic, C.; Fisk, Z.; Pagliuso, P. G.; Sarrao, J. L. Phys. Rev. Lett. 2001, 86, 5152-5155. (13) Paglione, J .; Tanatar, M. A.; Hawthom, D. G.; Boaknin, R.; Hill, R. W.; Ronning, F.; Sutherland, M.; Taillefer, L.; Petrovic, C.; Canfield, P. C. Phys. Rev. Lett. 2003, 91, 4. 91 (l4) Chevalier, B.; Gaudin, E.; Weill, F .; Bobet, J .-L. Intermetallics 2004, 12, 437. (15) Kanatzidis, M. G.; Pottgen, R.; Jeitschko, W. Angewandte Chemie-International Edition 2005, 44, 6996-7023. (16) Chen, X. Z.; Sportouch, S.; Sieve, B.; Brazis, P.; Kannewurf, C. R.; Cowen, J. A.; Patschke, R.; Kanatzidis, M. G. Chem. Mater. 1998, 10, 3202-3211. (17) B. Sieve; X. Z. Chen; R. Henning; P. Brazis, C. R. Kannewurf; J. A. Cowen; A. J. Schultz; Kanatzidis, M. G. J. Am. Chem. Soc 2001, 123, 7040. (18) Sieve, B.; Trikalitis, P. N.; Kanatzidis, M. G. Z. Anorg. Allg. Chem. 2002, 628, 1568-1574. (19) Chen, X. Z.; Larson, P.; Sportouch, S.; Brazis, P.; Mahanti, S. D.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 1999, 11, 75-83. (20) Zhuravleva, M. A.; Kanatzidis, M. G. Z. Naturforch B .' Sec. B 2003, 58, 649-657. (21) Zhuravleva, M. A.; Pcionek, R. J .; Wang, X. P.; Schultz, A. J .; Kanatzidis, M. G. Inorg. Chem. 2003, 42, 6412-6424. (22) Zhuravleva, M. A.; Evain, M.; Petricek, V.; Kanatzidis, M. G. J. Am. Chem. Soc 2007, 129, 3082-3083. (23) Chen, X. 2.; Small, P.; Sportouch, S.; Zhuravleva, M. ; Brazis, P.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 2000, 12, 2520-2522. (24) Lattumer, S. 13.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Chem. Mater. 2002, 14, 1695-1705. (25) Lattumer, S. E.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2003, 42, 7959-7966. (26) Lattumer, S. E.; Kanatzidis, M. G. Inorg. Chem. 2008, 47, 2089-2097. (27) Wu, X. U.; Lattumer, S. E.; Kanatzidis, M. G. Inorg. Chem. 2006, 45, 5358-5366. 92 (28) Wu, X. N.; Kanatzidis, M. G. J. Solid State Chem. 2005, 178, 3233-3242. (29) Salvador, J. R.; Gour, J. R.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2004, 43, 1403-1410. (30) Salvador, J. R.; Bilc, D.; Gour, J. R.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2005, 44, 8670-8679 (31) Salvador, J. R.; Kanatzidis, M. G. Inorg. Chem. 2006, 45, 7091-7099. (32) Salvador, J. R.; Hoang, K.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2007, 46, 6933 (33) Chondroudi, M.; Balasubramanian, M.; Welp, U.; Kwok, W.-K.; Kanatzidis, M. G. Chem. Mater. 2007, 19, 4769-4775. (34) Canfield, P. C.; Fisk, Z. Z. Philos. Mag. B 1992, 65, 1 117-1123. (35) Bud'ko, S. 1.; Islam, Z.; Wiener, T. A.; Fisher, 1. R.; Lacerda, A. H.; Canfield, P. C. J. Magn. Magn. Mater. 1999, 205, 53. (36) Fisher, 1. R.; Islam, Z.; Canfield, P. C. J. Magn. Magn. Mater. 1999, 202, 1-10. (37) Hundley, M. F.; Sarrao, J. L.; Thompson, J. D.; Movshovich, R.; Jaime, M.; Petrovic, C.; Fisk, and Z. Phys. Rev. B 2001, 65, 024401. (38) Macaluso, R. T.; Sarrao, J. L.; Moreno, N. 0.; Pagliuso, P.G.; Thompson, J. D.; Fronczek, F. R.; Hundley, M. F.; Malinowski, A.; Chan, J. Y. Chem. Mater. 2003, 15, 1394-1398. (39) Sakamoto, I.; Shomi, Y.; Ohara, S. Physica B 2003, 329-333, 607-609. (40) Bailey, M. S.; McCuire, M. A.; DiSalvo, and F. J. J. Solid Sate Chem. 2005, 178, 3494-3499. 93 (41) Benbow, E. M.; Lattumer, S. E. Inorg. Chem. 2006, 179, 3989-3996. (42) Klunter, W.; Jung, W. J. Solid Sate Chem. 2006, 179, 2880-2888. (43) Zaremba, V. I.; Dubenskiy, V. P.; Rodewald, U. C.; Heying, B.; Pottgen, R. J. Solid State Chem. 2006, 1 79, 891-897. (44) Tobash, P. H.; Lins, D.; Bobev, S.; Lima, A.; Hundley, M. F .; Thompson, J. D.; Sarrao, J. L. Chem. Mater. 2005, 17, 5567-5573. (45) Ehlers, G.; Maletta, H. Z. Phys. B 1996, 101, 317-327. (46) Kittel, C. Introduction to Solid State Physics 7th ed.; John Wiley & Sons, 1996. (47) Yoshida, H.; Ahlert, S.; Jansen, M.; Okamoto, Y.; Yamaura, J .; Hiroi, Z. Journal of the Physical Society of Japan 2008, 77, 8. (48) Yamamura, T.; Li, D.; Yubuta, K.; Shiokawa, Y. J. Alloy. Compd. 2004, 374, 226-229. (49) Yamamura, T.; Li, D. X.; Shiokawa, Y. Physica B-Condensed Matter 2003, 329, 559-560. (50) Li, D. X.; Donni, A.; Kimura, Y.; Shiokawa, Y.; Homma, Y.; Haga, Y.; Yamamoto, E.; Honma, T.; Onuki, Y. J. Phys. -Condes. Matter 1999, 11, 8263-8274. (51) Kittel, C.; Wiley: New York, 1968; Vol. 22. (52) Kasuya, T. Magnetism; Academic Press: New York, 1966; Vol. IIB. (53) Kasuya, T. Prog. Theoret. Phys. 1956, 16, 45-57. 94 CHAPTER 4 Flux Synthesis of Yb3AuGe21n3: an Ordered Variant of the YbAuIn Structure Exhibiting Mixed-Valent Yb Behavior 4-1. Introduction Intermetallic compounds of the ternary systems RE/TM/In (M = Cu, Ag, Au) include numerous new intermetallic phases that exhibit rich structural variety"2 and interesting physical properties.3 Some examples are CeAuIn,4'8 and the families REAuIn (RE = Eu, Gd-Ho, Yb),4‘7'9'13 and REAuzln.”‘M'18 In the latter family for example the members formed by light RE elements undergo a structural phase transition, while the heavy RE ones display magnetic transitions. YbAuzln is a intermediate valence (IV) compound19 that shows pressure induced transition from IV to trivalent magnetic states.”’l5 Further examples are the REzAuzln (RE = La-Gd and RE = Tm-Lu)20 which adopt two different structure types depending on the size of the RE, szTlen (TM = Cu, Pd, Au),21 and REAg21n(RE = Tb, Dy).22 An especially interesting set of compounds are the YbCu4+xIn|.x23'26 and their Ag, Au analogs”. This family has shown both mixed and intermediate valency characterized by a first-order temperature-induced isostructural valence phase transition. It also shows valence fluctuation induced by pressure or alloying and it belongs to the class of “light” heavy-fermion systems.”30 Increase of the In ratio in the RE/Au/In system leads to EuzAu3In4,3 ' REzAu3In5 (RE = Ce, Pr, Nd, Sm),32 REAuzlm (RE = La, Ce, Pr, Nd),33 EuAuInz,” 95 Indium as a flux has been widely used for the crystal growth of principally known binary or ternary phases?“ It has been little exploited as a synthetic medium 33'42'56 especially for quaternary compounds, although there is compared to Al and Ga, now an increasing interest in this approach.”62 Our work with In flux includes only a limited number of quaternary phases so far, such as the RE4Ni21nGe4 (RE = Dy, Ho, Er, Tm)” and RE7Co4InGelz (RE = Dy, Ho, Yb).56 After the rich chemistry revealed by the thorough examination of the ternary RE/Au/In system we decided to incorporate also a tetrelide such as Ge in order to search for more complex structures and compositions. This is analogous to the RE/TM/Al /Si or 40"“ Among the rare earth Ge and RE/TM/Ga/Ge or Si systems investigated previously. compounds, the Yb-based intermetallics which are considered as the electron hole counterparts to the isostructural cerium compounds, have received considerable attention for the past few years. This interest originates from their ability to exhibit various peculiar properties such as intermediate-valence, heavy fermion or Kondo behavior and unusual magnetism.“65 These properties are generally believed to arise from the strong hybridization (interaction) between the localized 4f electrons and the delocalized s,p,d conduction electronsf’é’67 Here we present the new compound Yb3AuGezln3, grown from In flux which crystallizes as an ordered variant of the YbAuIn structure and it is the first quaternary phase reported as an extension of the rich and extensively studied RE/Au/In system. The synthesis, crystal structure, and the study of the magnetic properties, X-ray absorption near edge spectroscopy (XANES), electrical resistivity, thermoelectric power and heat capacity measurements are reported. These studies suggest that Yb3AuGe21n3 is an intermediate or heterogeneous mixed-valence system. The results of the study of the 96 crystal structure refinement, magnetic properties, electrical resistivity, heat capacity and XANES experiments for the isostructural YbAuIn are also presented in an attempt to investigate the similarities and/or differences between the two compounds. 4-2. Experimental section Reagents: The following reagents were used as purchased without further purification: Yb, (in the form of powder ground from metal chunk, 99.9% Chinese Rare Earth Information center, Inner Mongolia, China), Au (pieces, 99.9% Alfa Aesar, Ward Hill, MA), Ge ( ground from 2-5 mm pieces 99.999% Cerac, Milwaukee, WI) and In (tear drops 99.99% Plasmaterials, Liverrnore, CA). Synthesis: Yb3AuGezln3 was obtained by combining 3 mmol of the ytterbium metal, 2 mmol gold, 3 mmol germanium and 15 mmol In in an A1203 (alumina) crucible under an inert nitrogen atmosphere inside a glove-box. The crucible was placed in a 13 mm fused silica tube, which was flame sealed under vacuum of 10'4 Torr, to prevent oxidation during heating. The reactants were then heated to 1000 0C over 10 h, maintained at that temperature for 5 h to allow proper homogenization, followed by cooling to 850 0C in 2 h and held there for 48 h. Finally, the system was allowed to slowly cool to 50 0C in 48 h. The reaction product was isolated from the excess In flux by heating at 350 0C and subsequent centrifugation through a coarse frit. Any remaining flux was removed by immersion and soniqation in glacial acetic acid for 48 h. The final crystalline product was 97 rinsed with water and dried with acetone. This method produced the target compound with ~ 90% purity and in a yield of ~ 90 % based on the initial amount of Yb metal used in the reaction. Main side products were very small amounts of YbAuGe and unreacted In metal. Several crystals, which grow as metallic silver rods were carefully selected for elemental analysis, structure characterization, and the physical measurements reported here. YbAuIn was prepared by direct combination of the reactant elements in their stoichiometric ratios in a Ta crucible under an inert nitrogen atmosphere inside a glove- box. The Ta tube was sealed under vacuum by Arc Welding and subsequently was sealed in a quartz tube under a vacuum of 10“1 Torr. The tube was then heated at 1100 °C where it stayed for 6 -24 hours and finally it was quenched from this temperature in liquid nitrogen. This method produced YbAuIn in mainly polycrystalline form but also in compact pieces of crystals in a yield of ~ 60 % and purity of ~ 97 %. Elemental Analysis: ngAuGezlm: Semi-quantitative microprobe elemental analysis was performed on several crystals of the compound using a JEOL JSM-35C scanning electron microscope (SEM) equipped with a Noran Vantage Energy Dispersive Spectroscopy (EDS) detector. Data were acquired by applying a 25 kV accelerating voltage and an acquisition time of 40 s. A typical rod-like crystal of ngAuGezlng is shown in Figure 1. The EDS analysis taken on visibly clean surfaces of the Yb3AuGe21n3 crystals gave the atomic composition of 32.95 % Yb, 10.92 % Au, 32.75 % In and 23.39 % Ge, which is in 98 very good agreement with the results derived from the single crystal X-ray diffraction refinement. YbAuIn: Semi-quantitative microprobe elemental analysis was performed on several crystals of the compound using a HITACHI MODEL S-2700 Scanning Electron Microscope (SEM) equipped with a light-element window Noran System Six EDS detector. Data were acquired by applying a 20 kV accelerating voltage and an acquisition time of 1 min. For the mainly polycrystalline YbAuIn the EDS analysis gave the atomic composition of 35.37 % Yb, 33.45 % Au and 31.18 % In in fairly good agreement with the single crystal X-ray diffraction results, though some pieces gave Yb rich content suggesting they may be impurities present. X-ray Crystallography: The X-ray intensity data were collected at room temperature using a STOE IPDS 2T (with additional capability of 26 swing of the detector) diffractometer with graphite- monochromatized Mo Km (,1 = 0.71073 A) radiation. The X-AREA (and X-RED and X- SHAPE within) package suite68 was used for data extraction and integration and to apply empirical and analytical absorption corrections. The structures of Yb3AuGe21n3 and YbAuIn single crystals were solved by direct methods and refined with the SHELXTL package of programs.69 A stable refinement for both compounds was accomplished only in the hexagonal space group P-62m. Data collection and structure refinement details are given in Table 4-1. The final atomic positions, equivalent isotropic displacement parameters and anisotropic displacement parameters are listed in Table 4-2 and 4-3. 99 To determine the phase identity and purity, powder X-ray diffractions pattern of Yb3AuGe21n3 were collected at RT on a CPS 120 INEL X-ray diffractometer with Cu Ka radiation, equipped with a position-sensitive detector and were compared to the pattern calculated from the single crustal structure refinement. For YbAuIn RT powder X-ray diffraction analysis was carried out on a PANanalytical X’Pert Pro MPD in Bragg- Brentano geometry with Co Ka radiation and an X’celerator detector. Table 4-1. Crystal data and structure refinement data for Yb3AuGe21n3 and Yb3Au3In3. Empirical formula Yb3AuGe21n3 Yb3AU3In3 Formula weight 1205.73 727.24 Temperature (K) 293(2) 293(2) Wavelength (A) 0.71073 0.71073 Crystal system Hexagonal Hexagonal Space group P-62m P—62m a, b (A) 7.3153(8) 7.7127(11) c (A) 4.4210(5) 4.0294(8) V(A3) / z 204.89(4) / 1 207.58(6)/ 1 Densitycalc(Mg/m3) 9.772 11.635 Absorption coefficient (mm'1)/ F(000) 67.086 / 500 94.272 / 594 0 range for data collection (°) 3.22 to 28.25 5.06 to 34.27 -9_<_hS9 -12£h512 Index ranges -9Sks9 -125k$12 -5 51 s 5 -5 S l S 6 Reflections collected / unique / R(int) 2272 / 213 / 0.0262 2949 / 363 / 0.1339 Completeness to 6’ (%) 99.2 99.5 Data/restraints/ parameters 213 /O/ 14 363 / 0/ l4 Refinement method Full-matrix least- squares on F2 Goodness-of-fit on F2 1977 1.192 Final R indices [1>20(1)] (Rl /wR2)a 0.0298 / 0.0746 0.0418 / 0.1039 R indices (all data) (R1 /wR2)" 0.0298 / 0.0746 0.0432 / 0.1046 Extinction coefficient 0.0012(6) 0.0037(9) Largest diff. peak and hole (e. X3) 1.723 and -1777 4.004 and -2994 1/ “R1 = lllFal 'IFcll/ZlFOI; sz =[ZWlFal -|&|}2/Z‘41Fa|2j 2; W =1/021F01} 100- 4 Table 432. Atomic coordinates (x 10 ) and equivalent isotropic displacement parameters 2 (A x 10 ) for Yb3AuGe21n3 and Yb3Au3In3. Atom Wyckoff x y z U(eq)a Yb 3g 4197(2) 0 5000 9(1) Au 1b 0 0 5000 15(1) Ge 2c 3333 -3333 0 8(1) In 3f 7512(3) 0 0 13(1) Yb 3g 4069(2) 0 5000 1 1(1) Au(l) 1b 0 0 5000 12(1) Au(2) 2c 3333 -3333 0 11(1) In 3f 7416(3) 0 0 10(1) aU(eq) is defined as one third of the trace of the orthogonalized UiJ tensor. Table 4-3. Anisotropic displacement parameters (A2 x 103) for Yb3AuGezln3 and 2 11 Yb3Au3In3. The anisotropic displacement factor exponent takes the form: -21t [h a* U + l2 .. +2hka*b*U ] Atom U11 U22 U33 U23 U13 U12 Yb 9(1) 8(1) 8(1) 0 0 4(1) Au 17(1) 17(1) 12(1) 0 0 8(1) Ge 11(1) 13(1) 16(1) 0 0 6(1) In 9(1) 9(1) 7(2) 0 0 4(1) Yb 9(1) 10(1) 15(1) 0 0 5(1) Au(l) 11(1) 11(1) 15(1) 0 0 5(1) Au(2) 9(1) 9(1) 16(1) 0 0 4(1) In 7(1) 7(1) 14(1) 0 0 4(1) 101 Magnetic Measurements: Magnetic susceptibility measurements for Yb3AuGezln3 were carried out with a Quantum Design MPMS SQUID magnetometer at Michigan State University facilities. EDS-analyzed crystals were soaked in ~ 6M of HCl acid for 15-30 min, washed out with water, and dried out in a dry oven. The crystals were then ground in open air atmosphere and sealed in Kapton tape which was inserted into the SQUID magnetometer. Temperature dependence data were collected between 3 and 400 K, for both zero field cooled (ZFC, on warming) and field cooled mode (PC, on cooling), with an applied field of 500 G. Field dependent magnetic measurements were acquired at 3 and 150 K with field sweeping from 0 up to 50 kG. Core diamagnetic corrections were applied. In order to study the magnetic anisotropy of the material, measurements were performed on several aligned single crystals oriented with the c-axis parallel and normal to the applied field of 2 kG. Field dependence measurements were also performed for both orientations at 5 K between 0 and 50 kG. These measurements were conducted at Northwestern University facilities. Additional magnetization measurements were conducted at Materials Science Division (MSD) facilities at Argonne National Laboratory (ANL) using a Quantum Design MPMS SQUID magnetometer equipped with reciprocating sample option (RSO) mode as well as a Quantum Design PPMS magnetometer. For these measurements crystals of Yb3AuGezln3 were soaked in glacial acetic acid and soniqated for 24 — 48 hrs, washed out with dried acetone and dried under the flow of nitrogen. Samples of YbAuIn were used without any further cleaning process. Subsequently, crystals were either ground inside a nitrogen filled glove-box or loaded randomly (or oriented) without 102 grounding into gelatin capsules, mounted in a plastic straw and affixed to the end of a carbon fiber rod. Multiple temperature and field dependent measurements were performed for both compounds at various fields and temperatures. X-ray absorption near edge spectroscopy (XANES): X-ray absorption near edge spectroscopy (XANES) experiments were performed in Sector 20, bending magnet beamline (PNC/XOR, 20—BM) of the Advanced Photon Source at the Argonne National Laboratory, IL, USA. Measurements at the Yb Lm edge and at ambient pressure were performed in the transmission mode using gas ionization chambers to monitor the incident and transmitted X-ray intensities. A third ionization chamber was used in conjunction with a copper foil to provide internal calibration for the alignment of the edge positions. Monochromatic X-rays were obtained using a Si (111) double crystal monochromator. The monochromator was calibrated by defining the inflection point (first derivative maxima) of Cu foil as 8980.5 eV.7o A rhodium-coated X- ray mirror was utilized to suppress higher order harmonics. The ngAuGezlng and YbAuIn samples were prepared both by mixing an appropriate amount of finely ground powder with BN and cold pressing them to a pellet as well as by dusting the finely ground sample on Kapton tape and stacking several layers (8-12 layers) together. Most of sample preparation procedures were carried out inside a glove box environment. Measurements were performed at a range of temperatures from 15 to 300 K using a closed cycle refrigerator. Data reduction and analysis were performed using Athena and Artemis software developed by Newville and Ravel.7| Care was taken to minimize thickness effects in the measurements. 103 Resistivity: For Yb3AuGe21n3 electrical resistivity was determined using a six probe technique in a standard 4He gas flow cryostat at Materials Science Division (MSD) facilities at Argonne National Laboratory (ANL). Heating was avoided by reducing the current, and hysteresis, caused by slight thermometer - sample temperature differences, was avoided by sweeping the temperature slowly. More detailed experimental description can be found elsewhere.72 Data points were taken during the cooling cycle from 302 to 2.48 K. Typical size of the rod-shaped crystals measured forYb3AuGezln3 was 0.66 x 0.12 x 0.08 mm. For YbAuIn electrical resistivity was measured as a function of temperature on single crystals. Electrical contact was made using silver paint and Cu wire directly on the crystals surface. Measurements were made for arbitrary current directions in the a, c-plane using a standard four point contact geometry (AC) in a Quantum Design Physical Property Measurement System (PPMS). Data points were recorded during the heating cycle at a temperature range of 1.8 — 274.3 K. Heat Capacity: Specific heat measurements of single crystals of Yb3AuGe21n3 and YbAuIn were performed by a Quantum Design PPMS commercial device, at Northwestern University facilities, in the temperature range of 1.8 -— 50.3 K by relaxation method using the “Two- Tau Model”.73 104 Thermoelectric Power: Thermoelectric power was measured using a SB-100 Seebeck Measurement MMR System, at Northwestern University facilities, in the temperature range between 310 and 710 K on a single rod-shaped crystal of Yb3AuGe21n3, The electrical contact for the thermopower measurement was made using silver paint with the sample mounted on an alumina stage. 4-3. Results and Discussion Reaction Chemistry: Crystals of Yb3AuGe21n3 grow in In flux generally as metallic silver rods and in a smaller portion as thinner needles. Figure 4-1(A) shows a seaming electron micrograph of a typical rod type Yb3AuGe21n3 crystal. Reaction byproducts were small amounts of unreacted gold which tends to wet the surface of the crystals as well as very small amounts of YbAuGe, which due to very different crystal morphology (polygonal shape) could be easily distinguished and removed when necessary. When other rare earth metals such as Ce, Sm, Eu, Dy and Pr were employed under the same reaction conditions we did not observe analogs of Yb3AuGezln3. Instead these reactions led to other quaternary phases which will be reported in future work. In contrast, the REAuIn family of compounds forms with most of the RE atoms including Yb.4 The YbAuIn compound was synthesized by direct combination of the reactants in primarily grey polycrystalline form and pieces made up from packed crystals, with the exemption of the formation of a few single silvery metallic crystals as needles. The main byproduct was recrystallized Ta from the reaction vessel. Attempts to generate the 105 YbAuIn phase by flux reactions failed to produce the target phase in a significant purity and yield as they are many competitive beAuzIny phases. Figure 4-1(B) displays an SEM image of an YbAuIn chunk. 350mm 11m 11m (A) (B) Figure 4-1. Scanning electron micrograph (SEM) image of (A) a flux-grown Yb3AuGe21n3 single crystal and (B) a compact piece of YbAuIn. Structure: Yb3AuGe21n3 crystallizes as an ordered variant of the YbAuIn structure4’” which can be explained in the following manner; in the quaternary compound Ge has substituted for one of the two Au positions of the ternary compound written as Yb3Au3In3. Both compounds adopt the ZrNiAl-type structure,74 which itself is a ternary ordered version of FezP,75 in the hexagonal space group P-62m. The overall structure of the quaternary compound as viewed down the c-axis is illustrated in Figure 4-2. Yb3AuGe21n3 can be 106 described as alternating layers of [Gezln3] and [Yb3Au] slabs that stack along the c-axis as it can been seen in the a,c view of the framework, Figure 4-3(A). Detailed descriptions of the two structural fragments are given below. The [Gezln3] slabs consist of regular planar triangles built up from three In atoms and slightly distorted planar pentagons composed of one In-In dimer and four In-Ge bonds, as can be seen in the a,b projection of this layer, Figure 4-3(B). Every triangle is surrounded by six pentagons (two regular and four distorted) thus forming an infinite network of three- and five-membered rings that extend in the a, b-plane and stack along the c-axis. The bond between the In atoms is 3.152(4) A which compares well to the In-In bonds found in the tetrameric segment of REAu21n433 ranging between 2.966(1) and 3.172(1); but it is shorter than the average In-In distance of 3.333 A in elemental indium,76 suggesting rather strong bonding. The In-Ge bonds at 2.7993(14) compare well to corresponding distances found in EuInGe77 and CazLiInGeg78 ranging from 2.75 to 2.876 A, but these are shorter than the ones found in the quaternary phase RE7CO4IDGC|256 (ranging from 2.9214(14) to 2.965(3) A) or in Ce3Ino,39Ge._H79 where they have the value of 2.99 A. In the [Yb3Au] layer of the structure the Yb atoms are arranged in a flat net forming comer-sharing triangles with Yb-Yb distance of 3.7996(8) A, see Figure 4-3(C). The Yb-Yb distance between two adjacent [Yb3Au] layers is equal to the c-axis at 4.4210(5) A. The three-dimensional arrangement that the rare earth atoms adopt in this structure type leads to three exceptional features: 1) The RE ions within the same layer form triangles so when it comes to antiferromagnetic coupling between nearest neighbours, this t0pology can cause frustration of the magnetic interactions. ii) The fact 107 that the magnetic RE atoms are stacked in [Yb3Au] layers that alternate with the non- magnetic Ge-In layers, can give rise to indirect exchange interactions. iii) The crystalline electric field surrounding the lanthanide ions frequently induces strong anisotropy, which leads either to Ising or XY spin behavior.”8| Examples of compounds adopting this arrangement are the families of REAuIn'O'IZ and RENiAl.82‘83 The Au atoms are isolated from one another and are found among the Yb triangles in the net at a Au — Au distance of 7.3153(8) A, which is equal to the a-cell parameter. With respect to the [Ge21n3] slab the [Yb3Au] layer is positioned so that the Yb atoms are in registry with the centers of the pentagons, while the Au atoms are in registry with the In triangles, see Figure 4-2. The bonding environment of the Au atoms is shown in Figure 4-4. As mentioned above the Au atoms are isolated from each other forming bonds only with In and Yb atoms. Each Au atom forms six bonds to In atoms, from which three belong to the [Ge21n3] layer above and three to the layer below the atomic Au plane at an equal bond distance of 2.8634(13) A, which agrees well with other reported Au-In bonds of other intermetallic compounds3"34. This arrangement makes for a regular trigonal prismatic geometry around the Au atoms. The rectangular faces of the gold-centered indium prism are capped by three Yb atoms in a trigonal planar mode, with Yb-Au bond equal to 3.0700(15), resulting in a coordination number (CN) of 9 for the Au atoms. A nearest neighbor environment with CN 9 is common for transition metal atoms in intermetallic compounds. The Ge atoms are also isolated from one another and exhibit the same coordination geometry with the Au atoms, but in this case the trigonal prismatic enviroment is formed by the Yb atoms and is capped by three In atoms in a trigonal 108 planar manner, Figure 4-4. The In atom is eight coordinate, bonded to two other In atoms as well as to two Au, Yb and Ge atoms respectively in an arrangement that could be described as distorted tetragonal prism, Figure 4-4. The coordination environment of the crystallographically unique Yb site is given in Figure 4-4. The rare earth atom is coordinated by 6 In atoms and 4 Ge atoms that gives rise to a pentagonal prismatic geometry, capped by a Au atom. An alternative view of the Yb3AuGezln3 structure is in polyhedral representation. Figure 4-5, depicts the connectivity of the Au-centered In trigonal prisms and the Ge- centered In planar trigons, as viewed in the a,b-plane. The In trigonal prismatic polyhedra are fused. They share both of their trigonal faces thus forming trigonal columns that extend along the c-axis, see Figure 4-6. These columns are aligned parallel to each other and every such column shares each In comer, in the a, b-plane, with two trigonal planes which are centered by Ge atoms. Overall six such trigonal planar polyhedra surround every trigonal prismatic column to build the three-dimensional [AuGeZIn3] framework. The Yb atoms reside within the void space among the polyhedra. Table 4-4 gives a list of selected bond distances for Yb3AuGe21n3 and YbAuIn. 109 Figure 4-2. The overall structure of Yb3AuGe21n3 as viewed onto the a,b-plane. For clarity the bonds to the Yb atoms are not drawn. 110 III .fVcI/ I\\ II A\ lfll—Vgn .I\\ .Iu\\ Figure 4-3. (A) Projection of the crystal structure of Yb3AuGeZIn3, viewed approximately down the b-axis, where the alternating layers of [Ge21n3] and [Yb3Au] are emphasized. (B) Projection of the [Ge21n3] layer onto the a,b-plane. (C) Projection of the [Yb3Au] layer onto the a,b-plane. The Yb atoms are connected with lines in order to emphasize the corner-sharing triangles. 111 HEM Figure 4-4. Coordination environment of the Au, Ge, In and Yb atoms. The coordination sphere cutoff is 3.5 A. 112 Figure 4-5. Polyhedral view of the Yb3AuGe21n3 structure featuring the connectivity of the Au-centered In trigonal prisms and the Ge-centered In planar trigons, in the a, b-plane. .9. r. 3 ~ ., 4" i Figure 4-6. Stacking of the Ge-centered In trigonal planes and Au-centered In trigonal prisms along the c-axis. The In trigonal prisms are fused, forming trigonal columns that extend down the c-axis. 113 Table 4-4. Selected bond lengths (A) for Yb3AuGe21n3 and Yb3Au31n3. Bond Yb3AuGe21n3 Yb3Au31n3 Yb-Au / Yb-Au(l) 3.0700(15) 3.0874(5) Yb-In 3.2815(19) 3.275(2) 3.4694(9) 3.4094(10) Yb—Ge 3.1131(4) Yb-Au(2) 3 0874(5) Au-In / Au(l)-In 2.8634(13) 2.8339(16) Au(2)-In 2.9033(15) Ge-In 2.7993(14) Yb-Yb 3.7966(8) 4.0521(16) Magnetic Measurements: Grinding in open air. Figure 4-7(A) shows the temperature dependence of the molar magnetic susceptibility (xm) of a ground sample (grinding process was performed in open air atmosphere) of Yb3AuGezln3 measured from 3 to 400 K with applied field of 500 G. The magnetic susceptibility data follow a modified Curie-Weiss law that includes a temperature independent component according to the equation x(T) = x0 + C / (T — 6p). )(0 includes the sum of the temperature-independent conributions, e.g. van Vleck paramagnetism and Pauli paramagnetism (due to conduction electrons). The effective magnetic moment ,ucff was deduced from the Curie constant C, (C = ,ucgz / 8). A nonlinear least-squares fit to this equation resulted in X0 = 3.2 x 10'3 emu/mol of Yb atom, Curie - Weiss constant of 6p = -1.5 K indicating antiferromagnetic interactions and an effective 114 moment of 0.52 #3 / Yb atom. The inset in Figure 7(A) shows the plot of 1/ (x - X0) versus temperature. The estimated effective moment of 0.52 mg, is only ~ 11.5 % of the value expected for the free-ion Yb3+, 4.54 mg. This indicates that the compound contains both Yb2+ and Yb3+ atoms. In order to confirm the presence of Yb3+ species in the title compound we performed XANES studies that are discussed below. The field dependence of the magnetization M(H) for Yb3AuGe21n3 ground sample at 3 and 150 K can be found in Figure 4-7(B). The data measured at 3 K exhibit linear behavior up to about 12 kG at which point the slope changes continuously until about 33 kG, where it becomes linear again but with a much shallower slope. No signs of saturation up to highest attainable field of 50 kG were observed. The magnetization curve taken at 150 K shows a very different picture. There is a strong field dependent response up to ~ 1.2 kG, which saturates at ~ 11 kG, while above that field M(H) becomes linear up to the highest obtainable field. This suggests that, there is probably a small ferromagnetic component in the ngAuGe21n3 compound which is part of the structure itself and not an extrinsic impurity component. It is possible that although the majority of the Yb atoms are in the Yb2+ state, there are small regions in the structure that are / . . . b2+ 3+ or even Yb3+ givmg rise to a occupied by Yb atoms having a non integer valence Y small number of magnetic moments. This small ferromagnetic component could explain the hysteresis that appears between the ZFC and FC magnetic susceptibility data in the temperature range of ~ 15 — 260 K an effect that is fully reproducible. 115 0.025 0.02 Xm (emu / mol) 0.015 0.01 0.1 .9 o 01 B -0.05 Magnetization (,u / mol) Temperature (K) A A AAAAAA: ataiat A A A AAAAAAAAAAI' I l I I I I I l 0 50 100 150 200 250 300 350 400 Temperature (K) I I I I I (B) ‘ 3K 'l ' 150K A A ” 'oooooooo ‘ 0.0043 ' j 0. I . q .0 '0 -0.004 p i .. 410‘ 0 410‘ I J I 4104 -210“ 0 2104 410‘ Field (G) Figure 4-7. (A) Temperature dependence of the molar susceptibility gm of Yb3AuGe21n3 (ground samples) with an applied field of 500 G. The inset shows the plot of l/ (xm - X0) versus temperature. (B) Magnetization data of Yb3AuGe21n3 collected at 3 and 150K. 116 “L I.“ Ali-I urn- Unground, randomly oriented crystals. We also performed temperature dependent molar magnetic susceptibility (1,") measurements for Yb3AuGe21n3 for a sample of randomly oriented crystals (placed in a kapton tape envelope, unground) measured between 3 and 400 K with an applied field of l kG, Figure 4-8. The data exhibit similar qualitative behavior. There is an apparent hysteresis between ZFC and FC data, at the temperature range of 15 — 340 K, but the x," values are smaller. A least- squares fit of the FC data with the modified Curie-Weiss law X(T) = 10 + C / (T — 6,,), resulted in X0 = 1.8 x 10'4 emu/mol of Yb atom, Curie - Weiss constant of 6,, = -0.86 K indicating antiferromagnetic interactions and an effective moment of only 0.13 pa / Yb atom. We see that the estimated effective moment is much smaller than the one found from the ground sample. This suggests that in the single crystal form Yb3AuGe21n3 has a smaller portion of Yb3+ moments. The inset in Figure 4-8 shows the field dependence of the magnetization M(H) for the single crystal sample of Yb3AuGe21n3 collected at 3K. The magnetic moment shows some strong dependence on the lower fields, roughly saturates between 24 and 37 kG, while the moment after 40 kG starts decreasing. This decrease at higher fields is probably due to the weak overall response of the paramagnetic moment and that the diamagnetic signal (from the background) at the higher field values becomes more significant. The magnetization data confirm the small portion of the Yb3+ moments in the sample. 117 T l r ' I l I 0.002 ”“5 ' 3K - E 0.002 - , \m .- .. c: .3 o 0.0015 5 0 ' d . a "3 \ .ts ' i z 7 5 E c-0002 - ' 3 go A 2 '~ ' E r .0... A >< C ‘ ‘ l I l _4 104 . 0 4 104 F1eld (G) A A A A A A A A A A A AAAA‘AAAA n AAAAA“A‘A‘AA ‘ ‘ ‘ A A ‘ I l l ”i I I 0 50 100 150 200 250 300 350 400 Temperature (K) Figure 4-8. Temperature dependence of the molar susceptibility Xm of Yb3AuGe2In3 (sample of randomly riented crystals) with an applied field of 1 kG. The inset shows the magnetization data of the same sample collected at 3 K and with fields sweeps from -50 to 50 kG. Magnetic anisotropy — unground, oriented crystals. Because the 3D arrangement of the RE atoms in the ZrNiAl-structure type ofien induces strong anisotropy, that could lead to interesting phenomena such as Ising or XY spin '0‘82 we measured the magnetic susceptibility parallel and normal to the c-axis of behavior, crystals of Yb3AuGe21n3. Several single crystals were aligned together so their c-axes were nearly parallel. From Figure 4-9 it’s obvious that the material is indeed magnetically 118 anisotropic. When the c-axis is oriented parallel to the applied field the material appears nearly diamagnetic above 60 K while when it is aligned normal to the field it exhibits almost temperature independent (pauli paramagnetic like) behavior which tends to a small increase towards higher temperatures. The magnetization curve measured at 5 K, see Figure 4-10, for the parallel orientation, shows linear dependence up to 22 kG. Beyond this point the slope starts to change with no saturation up to 50 kG. Finally, the magnetization with the field normal to c-axis is higher in magnitude and exhibits linear response up to 2 kG, followed by a change in slope at ~ 4 kG. The moment at 50 RG is 0.08 mg / mol more than the corresponding one of the parallel orientation. 0.016 0.012 ”'5‘ E \ 0.008 :3 E 3 ' 7 E >< 0.004 a 0 L L J‘ZVVI vvviv "VV:M. 0 50 100 150 200 250 300 Temperature (K) Figure 4-9. Temperature dependence of the molar susceptibility )(m of Yb3AuGe21n3 on single crystals, oriented with the c-axis parallel (circles) and normal (rhombi) to the applied field of 2 kG. 119 0.04 . . u u u - 0 H_Lc , .. c: . H//c . o E 0.02 - + , °° ' - \ .0 .0 m 0. 0'. 3 1- O .0 u .0 s: O .3 0 - - (U 0 .7?) ' 0'... ‘ g) .... ... «3 -0.02 - ' .o’ . E . . .0. . O - O _004 1 4 L 4 I 1 4 1 410 -210 0 210 410‘ Field (G) Figure 4-10. Field dependence magnetization measurements for both parallel and normal orientations measured at 5 K between -50 and 50 kG of applied fields. Magnetic Measurements under Variation of Experimental Parameters: In our efforts to further explore the magnetic properties we tried to study the magnetic behavior of Yb3AuGezln3 with measurements where various experimental parameters were adjusted. Our first attempt was to study the magnetic response of a sample initially consisted of randomly oriented crystals and subsequently after the crystals were ground in a inert atmosphere inside a N2 filled glove-box. The grinding process in a inert atmosphere was incorporated in order to avoid possible oxidation of the sample especially of the Yb species. We additionally changed the cleaning process of the crystals before the measurements, since the initially used HCl acid is considered a rather harsh and strong acid. In the following measurements the selected crystals were further 120 treated with glacial acetic acid and soniqation for ~ 24 - 48 days and then consequently washed with dried acetone and dried out under N2 atmosphere. Another experimental parameter that was tested was the temperature rate (K / min) of the initial cooling from room temperature down to lowest temperature of 2 K as well as the rate during data collection. Unground single crystals -- fast cooling. Figure 4-1 1(A) shows the temperature dependence of the magnetic susceptibility (xm) of an Yb3AuGezln3 sample of single crystals loaded randomly in a gel-cup and measured between 2 and 280 K with an applied field of 0.5 kG. The sample was zero field cooled from RT down to 2 K with a rate of 10 K / min (fast cooling) and the data were collected with the same rate (and settle mode). The data show again a hysteresis between the ZFC and F C at a temperature range of 60 - 280 K, see inset. A least-squares fit of the data with the modified Curie-Weiss law Xm(T) = x0 + C / (T— HP), resulted in 10 = 1 x 104 emu/mol of Yb atom, Curie - Weiss constant of 6p = - 1.7 K indicating antiferromagnetic interactions and an effective moment of 0.21 ,uB / Yb atom. This gives a 4.7 % of the theoretical value for Yb”; Ground inside N2 glove-box crystals — fast cooling. The molar magnetic susceptibility xm(T) data of the Yb3AuGe21n3 sample afier it was ground inside a glove- box, are given in Figure 4-11(B). As it can be seen, the magnetic data exhibit a remarkably different behavior. At ~ 145 - 150 K there is a sharp change in the slope, suggesting the onset of a ferromagnetic transition, while a divergence between the ZFC and FC data starts to occur. Additionally, the ZFC curve exhibits a crossover of the FC curve between 150 and 80 K. Below 80 K the divergence between ZFC and FC mode becomes maximum. An additional feature of a small cusp centered at ~ 180 K also 121 appears. This behavior was fully reproducible for ground samples were the grinding process was performed inside glove-box. 510'3 , , , . . . . (A) ’ Xm (0.5kG fast crystals) 410'3 ,- 510“ , , 3 -3 E 310 . \ 4 o a 410 L0... 0) -3 ....‘ d v 210 o, , . RE 3104. ....o. h ...::.o. . 1 10.3 ...::Q .. d 210‘ "any 100 160 200 250 uncommon»- l l I I I r I I l Xm(1kG fast ground) O O N A 01 oo '4 I '- 51 . O - 1- I I A 0.2 - (B) 1 '3 .I.- E I \ 0.15 " I. - .1 :3 I 8 -« ZFC I 0.1 - >< 0.5 " 0 LI 1 1 m 1 .. 7'” 0 50 100 150 2(1) 250 300 350 400 Temperature 00 Figure 4-13. Temperature dependence of the molar susceptibility )(m of Yb3AuGe2In3 with an applied field of 0.5 and 1 kG and temperature rates of 10 K / min (fast cooling) and l K / min (very slow cooling) (A) for a sample of randomly oriented crystals (B) same sample after grinding inside a nitrogen filled glove-box. 128 Unground single crystals - slow cooling. The field dependence of the magnetization M(H) data for both samples of Yb3AuGe21n3, single crystals and ground and under slow cooling, are given in Figures 4-14(A) and (B) respectively. For the magnetization data of the single crystals sample the temperature of 65 K was chosen in order to study the magnetic response in a temperature where the ZFC and FC data exhibit hysteresis in the Xm(T) data. The magnetic moment shows a linear response to the field up to ~ 20 kG. At higher fields there is a hysteresis loop up to about 50 kG, at which point the magnetization curve becomes linear again. This suggests that at 65 K where the ZFC and FC differ there is probably a ferromagnetic component in the system already before the crystals are ground. Ground crystals inside glove-box — slow cooling. Figure 4-14(B) shows the magnetization M(H) data after the grinding of the sample measured at 2 K and 200 K. The curve at 2 K exhibits a clear hysteresis loop for both negative and positive values of the field, which is a typical magnetic response for ferromagnetic systems. Above the field of ~ 27 l(G the hysteresis loop disappears the moment starts to saturate. At the highest applied field of 60 kG, the moment reaches a value of 0.45 #3 / mol which is only 7 % of the theoretical value for three Yb3+ atoms. In the M(H) data measured at 200 K (dashed line) the slope of the curve continuously changes and becomes linear at ~ 30 kG. At the field of 55 k0 the moment has a value of 0.37 #3 / mol, which is consisted with decreased saturation moment expected at higher temperatures. The inset shows the low field region data. The magnetization data support the assumption that there is a higher amount of Yb3+ species in the ground form of the sample and that the system goes through a magnetic phase transition that seems to be of ferromagnetic nature. 129 '—~—.- ..- "‘4 B Magnetization (u / mol) Magnetization (,u / mol) 0'003 —65K crystals slow] 1 0.002 - 0.001 4 0 I 4 I 4 I 4 l 4 J 4 4 0 110 210 310 410 510 610 Field (G) 05 1 I I I 1 I I —2K ground slow 2 . ° ° ' ' '200K ground slow 2 """"""" (B) m 0 l- _05 l 4 l I l J l .3104 4:104 o 4104 8104 Field (G) Figure 4-14. Magnetization data of Yb3AuGe21n3 collected at 2, 65 and 200 K and with a temperature rate of 1 K / min (A) for a sample of randomly oriented crystals (B) same sample afier grinding inside a nitrogen filled glove-box. Inset shows low fields region. 130 We also tried to investigate the magnetism of the YbAuIn compound under similar experimental conditions applied for the Yb3AuGe21n3 compound, hoping that it will help us in a better understanding of the intriguing results that we got from the study of the magnetic properties of the quaternary phase. Under this scope, measurements of both single crystals (or compact pieces of crystals) and ground samples (in open air and inside a glove-box) were used for fast as well as slow cooling temperature rates. Ground crystals in open air. Figure 4-15 shows the temperature dependence of the molar magnetic susceptibility (gm) of a ground sample (grinding process was performed in open air atmosphere) of YbAuIn measured from 2 to 400 K and with an applied field of 1.8 kG. Qualitative the X,,,(T) data display similar behavior with the ground in open air sample of the isostructural Yb3AuGe21n3, in that there is no transition but instead there is a small hysteresis between ZFC and PC (not apparent in the plot due to the scale of the low temperature region) roughly at the region of 15 — 250 K and above ~ 50 K the moment is only weakly temperature dependent. A nonlinear least-squares fit to this equation of the F C data up to 175 K (higher temperature data were excluded due to increased noise) resulted in X0 = 5 x 104 emu/mol, Curie - Weiss constant of 6,, = -3.5 K indicating antiferromagnetic interactions and an effective moment of 0.68 fig / Yb atom, which is about 15 % of the theoretical value for a free Yb3+ atom. The isothermal magnetization for the same ground sample of YbAuIn measured at 2 K can be found in the inset of Figure 4-15. The magnetization increases gradually with applied external field, which is characteristic of the paramagnetic state; and no sign of saturation is observed up to maximum applied field of 55 kG. Both susceptibility and low temperature magnetization measurements for a ground in open air atmosphere sample of 131 YbAuIn exhibit similar behavior with the corresponding ground sample in open air of Yb3AuGe21n3. Both materials exhibit paramagnetic behavior with no observed magnetic ordering but with a distinct, reproducible hysteresis between ZFC and FC data. I I j I I I I I 1 10-2 I I I I : O. T E 0.04 i ,. . 8 10'3 \m _ - e “ . .. 3 if” g .5 o- it - E 6 10-3 ‘5 Cf - \ .5. ,. 5 -l 3 4 1 0-3 an -0.04 I- q C; L; d . E E o O V N LO. ‘ i n I l n l - -3 .4104 o 4104 2 10 Field (G) ~ ' A A A ‘ I A ‘ k 0 10° . ‘ ‘5‘“:3- f“ {‘33:}: A: .. l l I I L I I I 0 50 100 150 200 250 300 350 400 Temperature (K) Figure 4-15. Temperature dependence of the molar susceptibility Xm of a ground in open air YbAuIn sample, with an applied field of 1.8 kG. The inset shows the magnetization data of the same sample collected at 2 K and with field sweeps from -55 to 55 kG. 132 Ground crystals inside glove-box. In Figure 4-16 two samples of YbAuIn are examined, one where crystals and compact pieces of crystals where ground inside a N2 filled glove-box and one where bigger pieces where just broken into much smaller ones by slightly hitting with a pestle in a mortar (in open air). Both samples were cooled from room temperature down to 2 K with the fast (10 K / min) temperature rate and the same rate was used during data collection. Ground inside glove box sample - fast cooling. The thermal variation of the susceptibility Xm(T) of the ground sample (open rhombi) of YbAuIn measured with 1 k0 applied field, given in Figure 4-16(A), differs remarkably from the ground in open air sample, in a similar way observed for the quaternary phase. The system seems to also undergo a ferromagnetic transition that onsets at ~ 145 - 150 K, as is evident by the steep change in the slope, which also coincides with the beginning of the ZFC and FC data divergences, as well as with the crossover of the ZFC curve of the FC curve that continues until 80 K. Below 80 K the difference becomes maximum as the ZFC curve after a peak starts going down, while the FC curves keeps rising to higher 1," values. The additional feature of a small cusp centered at ~ 180 K is also present. Crashed pieces - fast cooling. The susceptibility x,,,(T) of the sample consisting of crashed pieces (solid triangles) displays quite similar behavior, see Figure 4-16(A). Even though the overall increase of the moment is much smaller than in the ground sample, it still goes through a ferromagnetic transition. In this case, the transition is much broader and it starts at ~ 135 - 140 K, while the ZFC curve crosses over the FC curve until ~ 90 K (see inset). The biggest difference from the ground sample is in the ZFC curve behavior below 90 K. The ZFC data instead of going down towards smaller 133 susceptibility values, after the crossover they show a plateau until ~ 35 K and then they continue rising up to higher susceptibility values, even though they still diverge from the corresponding F C data. A very small cusp at 180 K also still appears. The isothermal magnetization for both ground (solid line) and crashed pieces (dashed line) samples of YbAuIn measured at 2 K, are given in Figure 4-16(B). For the ground sample the moments are rapidly aligned with the application of very small fields while hysteresis loops appear for both negative and positive fields, confirming the ferromagnetic state of the material. The highest applied field of 55 k0 is not enough to saturate the spins and the moment reaches only a value of 0.1 pg/ mol. The magnetization of the crashed pieces sample (dashed line) displays also a stronger field response at very small fields and a very small hysteresis at higher ones, but at the maximum applied field the moment is very small. 134 I I I I I I I 0.05 (A) O xm (lkG ground fast) - (be; A )(m (l.5kG hit pieces fast) 0.04 , — . .C.‘ ‘ FC _3 . ' ' ' O ( ' 9 10 | ‘. . E -. . ‘. . 3 0.03 - yr). 7103 A. a . f‘ "o -i - E - (373$) t ‘3‘ ‘ . 3 O 5 10'3 “ a E 0.02 ZFC 1'. h “ ‘‘‘‘ :5 ' . >< ' fl . . 0: 3103. 1 . ‘ .2, ,. " o 100 200 O . 0 1 FC k) (3m)? - :::‘A“‘ OK? ZFC ‘mAAAAAAAAAAAI. O 7 I 4 I I I I I 0 50 1 00 1 50 200 250 300 350 400 Temperature (K) 01 P I I I I I I - ----- 2K hit pieces fast —2K ground fast .0 o 01 T (B) B Magnetization (,u / mol) .6 8 -0.1 l- . . l 0. I 210‘. 410‘l -610‘ .410‘ -2104 o 2104 410‘ 6104 Field (G) Figure 4-16. (A) Temperature dependence of the molar susceptibility Xm of YbAuIn of a ground sample and hit pieces one, with applied fields of 1 and 1.5 kG, respectively and fast cooling. Inset shows low temperature data for pieces sample (B) Magnetization data of both samples collected at 2 K and field sweeps between -55 and 55 kG. Inset shows low positive fields region. 135 In the next measurements we tried to study the difference in the magnetic response of a sample consisted of random compact pieces of YbAuIn crystals as they came out of the reaction vessel without any grinding or crushing and after the pieces were ground in an inert atmosphere of a glove-box. Measurements were performed for both fast cooling (300 to 10 K with 10 - 12 K / min and down to 2 K with l K / min rate) and slow cooling (300 to 2 K with 1 K / min rate). During data collection the sweep mode was used with 1 K / min temperature change. The measurements were performed with a PPMS magnetometer (generally smaller sensitivity compare to SQUID measurements. Unground randomly oriented pieces, slow / fast cooling. Figure 4-17 shows the temperature dependence of the molar susceptibility xm of YbAuIn for the sample of randomly oriented pieces for fast (open circles) and slow (solid trigons) cooling rates. For both rates the sample seems to appear as paramagnetic, similar to the behavior for random single crystals of the Yb3AuGe21n3 compound, with a much more distinct hysteresis for the fast cooling data. .Light ground crystals inside glove-box, slow / fast cooling. The susceptibility Xm(T) data measured again for both fast and slow cooling after the same sample was slightly ground inside a glove-box, are displayed in Figure 4-18. The sample for both cooling rates shows practically the same behavior and exhibits the ferromagnetic transition that was seen in the previous ground samples (inside the glove-box) but some new features are also observed. Comparing to the data given in Figure 4-16(A) (measured at a SQUID), the hysteresis between the ZFC and FC data starts at 180 K, which coincides with the cusp found in the previous measurements and is followed by the ZFC curve crossing over the FC one at ~ 135 K until ~ 90 K. Below this temperature the 136 curves follow the same behavior as in the ground sample in Figure 4-l6(A). Furthermore, we notice a jump in the susceptibility for both cooling rates measurements at about 235 — 240 K, which coincides with the sharp and clear ferromagnetic transition that the ground sample of the Yb3AuGezln3 phase showed when it was measured at very slow cooling as well as data collection temperature rate (Figure 4-13(B)). Stronger grinding. In order to examine if the strength of the grinding process has any effect on the observed transition, we reground the previous lightly ground sample described in the previous paragraph but this time harder and for longer time. The susceptibility Xm(T) data of the reground sample (solid squares) are also presented in Figure 4-18. The reground sample measured under slow cooling rate gave the same qualitative behavior but the susceptibility was increased. 0.0135 ' ' ' j ‘ . 1‘ XmUkC’ fast) . ‘ x (lkG slow) A 00125 m - “'5 E E 00115 8, >~< . ZFC 0.01 - . xm 250C} ){m last l kG . )(m slow I kG C? O Xm 500G a i , \ XIII ~ 00 l‘ 5 E lF-lii"; Cl) v E O N 0.2.. n o ‘0 . .. . ’W . ~ ~ I I I I I 0 50 100 150 200 250 300 Temperature (K) Figure 4-19. Temperature dependence of the molar susceptibility Xm of a ground sample of YbAuIn of (A) ZFC, FC and FCW modes at l kG field (slow / fast cooling) and (B) curves in (A) and additional FC / FCW modes at 50, 150, 250 and 500 G fields. 140 Pressed pellet. The last measured ground sample was also pressed into a pellet and part of the pellet was measured with 1 kG applied field and with fast cooling rate. The thermal variation of the susceptibility of the pellet is given in Figure 4-20. The corresponding 1 kG data from Figure 4-19 are also plotted for comparison. As in the case of the pellet sample for the Yb3AuGe21n3 compound (Figure 4-13), besides the decrease in the susceptibility values, there was no significant change in behavior, comparing to the data before the sample was pressed into pellet. The only qualitative difference that can be observed is that the ZFC curve does not crossover the FC curve significantly any more. I I I I I 0.03 ’ Xm (ground fast) .. <7 Xm (pellet fast) 0.025 - .. ‘3 E :3 E 3 E >< 0 50 100 150 200 250 300 Temperature (K) Figure 4-20. Temperature dependence of the molar susceptibility Xm of a ground sample of YbAuIn and after pressing it into a pellet for ZFC, FC and FCW modes at l kG applied field and after fast cooling. 141 Unground specific oriented pieces. After investigating the magnetic behavior of YbAuIn for ground samples (outside and inside the glove-box) and random pieces the next logical step was to try to align some pieces into a specific orientation. For the following measurements a big compact piece was chosen as a base, and a few more crystals were placed on top of it with the help of a thin layer of high vacuum grease. The pieces were oriented so that the c-axis was parallel to the applied field. It should be noted here, that even though care was taken so that the selected compact pieces were consisted of mainly parallel aligned crystals, however within those pieces some variation of the crystals orientation did exist. In other words, the chosen orientation was achieved only in an approximation. Additionally, although the whole composite of the big and smaller pieces was tightly packed inside a gelatin-cup, small movement of the smaller pieces during the various measurements cannot be completely excluded. Magnetic susceptibility measurements for the composite sample were performed for various fields, as well as magnetization measurements at multiple temperatures for both fast and slow cooling rates. These conditions were the same as for the ones described for the previous measurements included in Figures 4-17 - 420. Slow / fast cooling. Figure 4-21 shows the temperature dependence of the molar magnetic susceptibility xm(T) of the YbAuIn oriented pieces with applied fields of 1 and 5 kG for both fast and slow cooling profiles. Both ZF C and F C modes were measured. As it can be seen more clear in the inset, which contains only the low temperature data, an apparent ferromagnetic like transition appears only for the slow cooling rate for both measured fields of 1 and 5 kG, that starts at ~ 70 and 80 K, respectively. Significant divergence between the ZFC and FC data also occurs after the onset of the transition. The 142 l kG data under fast cooling, even though they exhibit a small hysteresis between the ZFC and FC curves below ~ 65 K there is no obvious and sharp transition. A possible weak and broad transition that could start taking place at 65 K could be hindered by the peak at 60 K, which also appears in all the measurements, and is due to an artifact of the PPMS magnetometer used for the experiment. I I I I I 0.35 016 E , , , . ' h” . ' 1m (lkG fast) 0.3 ’ —. o b 0'12”; . D Xm(lkG slow) A o o _ ~ ‘ '6 0.25 1 .\ ,1 O. [m (5k(l slow) E 0.08 . . g _ X (SkG fast) \ 0.2 . . LC ’0. m a ' " . Fur ...°o o. ”:1: ’Ooo.,..o..... 3 O. 15 0.04 . .... rrtm'r2'rl‘nl _ ‘ O. E . ..°¢o««o«”m;”‘00 . >< ‘ ia-n'Q-{fij ;. 0.1 , ~ . - 0.05 250 100 150 200 300 Temperature (K) Figure 4-21. Temperature dependence of the molar susceptibility Xm of YbAuIn of a sample of compact pieces with crystals approximately oriented with c-axis parallel to the applied fields of 1 and 5 kG for fast and slow cooling temperature rates. 143 Magnetization at various temperatures for slow / fast cooling. Magnetization measurements for the same sample at various temperatures and for both slow / fast cooling are given in Figure 4-22. For the temperatures of 2 and 65 K that are measured for both cooling rates we see different response of the moment with the field for each cooling rate. The slow cooling magnetization curve at 2 K increases gradually with the applied field and does not seem to saturate up to 50 kG, where it reaches a magnetization value of 0.25 ,uB/ mol. On the other hand in the fast cooling corresponding curve, we see a decrease in the overall moment value and much weaker field dependence, while a field of about 40 kG is enough to start saturating the moments. At 50 kG the magnetization reaches the very small value of 0.068 )uB/ mol. The fast cooling curve at 40 K, which is below the ferromagnetic transition seen in the susceptibility data, shows a small increase of the moment until ~ 2.5 kG and then it stays roughly unchanged with a very small overall moment. Similar picture is observed for the fast cooling data at 100 K, which is above the transition. A weak field dependence until 2 kG is followed by a slightly decreasing moment, which after 5 kG it has a negative value. The slow cooling magnetization data at 65 K, which is within the transition temperature range, exhibits an evident hysteresis loop confirming the ferromagnetic transition observed in the susceptibility data. Additionally, in the increasing field cycle only there seems to be a metamagnetic like transition at ~ 16 kG where the moment starts showing a stronger field dependence, with no signs of saturation up to the highest attainable field, where it reaches a value of 0.23 in; / mol. In the fast cooling data at 65 K even though the overall magnetization is much smaller than the slow cooling one, there is still a hysteresis loop 144 between increasing and decreasing field curves. The magnetization at 50 kG is only 0.039 pB/ mol, with no observed saturation. 0.28 - l ' '- ' 2K fast 9 l- I 40K faSt . .- g 0.24 ’ 65K fast . . *2. \ 02 _ l00K fast ,_ ‘— A A: - ca ‘ " 2K slow an”; A A ‘2 0.16 _ ‘ 65Kslow *. a.“ ‘e . .9 g 0.12 - ‘:/ . E a, 0.08 . / "_ a 000 ...‘ .0... 2 0-04 l- -“ 30"... .000... "‘ :zzzzztt*“ 0 giggiulll!fl!!!g!!g§% 0 110 210 3104 4104 510‘ inadoG) Figure 4-22. Comparison of fast/slow cooling magnetization data at various temperatures for the YbAuIn sample of compact pieces with crystals approximately oriented with c- axis parallel. Magnetization at various temperatures for slow cooling. Complementary field dependent magnetization measurements for the same sample were performed for only the slow cooling rate at additional temperatures, see Figure 4—23. The 2 K data show again a gradual increase of the moment with the field and no saturation up to 70 kG, where it reaches a value of 1.4 pg / mol. At 10 K the magnetization increase linearly with the 145 applied external field and reaches a value of 0.52 pB/ mol at 56 kG. The magnetization measured at 20 K even though it still responds linearly to the field, surprisingly it reaches higher overall values with almost 1 ,uB/ mol at 56 kG. The magnetization curves at the next two temperatures of 30 and 40 K show very small positive or negative values of moment and stay roughly stable, within the sensitivity of the instrument, up to the highest applied field. When the temperature was raised to 50 K, the magnetization started reaching higher positive values with linear response to the field and got a value of 0.38 #3 / mol at 56 kG of applied field. At 65 K data were collected for a complete cycle, with the field going from positive values to negative ones (not all data included in the plot) and then back to positive. At this temperature a hysteresis loop appears for the positive region of fields, while noticeably afier the negative fields region when the field was switched back to positive values the magnetization data did not coincide with the ones collected the first time of positive applied fields. It is worth mentioning at this point, when comparing with the data plotted in Figure 4-22 for the same temperatures the absolute magnetization values are not the same for the same applied fields. This could be possibly due to some sort of a “memory effect” that could arise from the history preceding every measurement, meaning the temperature, the cooling rate and the highest applied field that was used. 146 1.5 I W I T I O 0 2K 0 O I 10K 0 2 9 0 20K 3 O o 0 g 1 h V 30K - o g _ 40K 000.0 . . : m 4. 50K 0er .0 O . o o 0 65K 0e0,o:'..' 75K e0 ,0: 0 - Magnetization (u / mol) .9 U1 0 2104 4104 6104 8104 Field(G) Figure 4-23. Comparison of slow cooling magnetization data at various temperatures for YbAuIn sample of compact pieces with crystals roughly oriented with c-axis parallel to applied fields. From all the measurements described above, we have seen some intriguing features in the magnetic properties of both Yb3AuGe21n3 and YbAuIn compounds. For both compounds there are some remarkable differences in the magnetic response among samples consisting of random or oriented crystals and ground samples for which the grounding process was carried out in the open air or in a inert atmosphere of N2 filled glove-box. The open air ground samples seem to be paramagnetic with a characteristic hysteresis between ZFC and FC data. On the other hand, the inside the glove-box ground 147 samples exhibit surprisingly a ferromagnetic transition and for most samples the onset of the transition is followed by an unusual ZFC curve crossover of the FC one. This behavior is fully reproducible and it has been observed by measurements performed in various samples and instruments. Furthermore, the strength of the grinding process seems to play a role in the overall amount of the measured magnetic moment. Additionally, the temperature rate of the initial cooling from room temperature down to 2 K as well as during collection time proved to play a decisive role in some cases for the occurrence of the ferromagnetic transition or the temperature that takes place. Unfortunately, at this point we are not able to fully understand and explain the magnetic behavior of the two compounds. Further study of this behavior, with the help of additional experimental techniques are necessary in order to clarify the observed properties. However, we could perhaps speculate on two possible explanations. In one of them, the two Yb-based compounds would exhibit a flexible and fluctuating Yb valence state, and the application of strain and/or pressure by the grinding process could perhaps induce an increase in the Yb3+/Yb2+ ratio that would lead to a new magnetic phase. Alternatively, the two systems could be some sort of dilute spin systems, in which the few existing spins intrinsically are dispersed throughout the crystal and they are not able to see each other, in order to lead in any kind of magnetic ordering, thus behaving as paramagnets. In this case the application of strain and/or pressure could not necessarily lead to an increase of the Yb3+ component, but instead force the spins to accumulate in small areas, forming small ferromagnetic domains. In those domains the more concentrated spins could perhaps be able to see each other with the application of a field, 148 thus leading to a ferromagnetic ordering. Figure 4-24, gives a hypothetical schematic picture for the second suggested theory. E Kagome lattice of Yb atoms I _ I l A A v A v H V Dilute paramagnet Ferromagnetic domains 7 / V Figure 4-24. Schematic picture of the hypothetical accumulation of spins forming small ferromagnetic domains. 149 Tables 4-5 and 4-6 summarize the main features observed in the magnetic measurements for Yb3AuGe21n3 and YbAuIn, correspondingly. Table 4-5. Summary of the magnetic behavior for various samples of ngAuGezln3. Sam le ty e ZFC / F C Magnetic Slow / fast cooling Grinding p p hysteresis behavior rate effect strength girround in open yes Para- not tested not tested . stronger ground in yes, below _ very slow rate . . glove-box transition Ferro higher transition T grinding —> higher moment random crystals yes Para- Slow —) higher pm oriented crystals Para— (low T) (H//c) no Diam- (high T) not tested 314.116??? crystals yes Para— not tested Table 4-6. Summary of the magnetic behavior for various samples of YbAuIn. Sam le ty e Magnetic Slow / fast cooling Grinding p p behavior rate effect strentgh ground in open air Para- not tested not tested stronger ground in glove-box Ferro- Not big difference grinding —) higher moment random crystals Para- Not big difference Only slow shows . F erro- clear transition & oriented crystals (H // c) Para- big difference in magnetization data 150 XANES Measurements at Ambient Pressure: To further probe the Yb valence state in ngAuGezln3 and YbAuIn we performed X-ray absorption measurements at the Yb Lug-edge. The near-edge spectra for both compounds obtained at temperatures of ~15 - 18 K and 300 K and at ambient pressure showed no significant difference between the two temperatures, suggesting that the Yb valence remained stable in the measured temperature range. The spectra at 295 and 300 K (room temperature) for Yb3AuGezln3 and YbAuIn, respectively, are given in Figure 4-25. The main absorption peak (white line resonance) of the spectrum for both spectra is centered at ~8941.5 eV, which is attributed to divalent Yb atoms.”86 The spectra also revealed the presence of weaker feature (shoulder) at ~8949.5 eV, indicating that some trivalent Yb is also present.”86 Since in both compounds under study there is only one unique crystallographic Yb site (as determined by the time scale of diffraction), there could be two plausible scenarios; one in which Yb3AuGezln3 and YbAuIn could be classified as an intermediate valence (IV) compounds with all Yb atoms having a non- integer valence, and a second where the materials are heterogeneous mixed-valence (MV) compound, in which the Yb atoms alternate between 2+ and 3+ state in various unit cells in the lattice. The relative amounts of the two electronic configurations were determined by decomposing the normalized Yb XANES into a pair of arc-tangents (representing the edge step) and Lorentzians functions (representing the white line resonance). Fitting of the data with the above technique for Yb3AuGe21n3, resulted in ~ 85.2% of Yb2+ and ~ 14.8% of Yb3+ which leads to an average Yb valence of ~ 2.15. For YbAuIn, similar analysis led to an average Yb valence of ~ 2.22. In the case of the YbAuIn however, 151 while majority of the Yb is present in the intermetallic state, a careful inspection and analysis of the EXAFS indicates that the sample might also contain ~ 3 - 5% trivalent oxide impurity component. Taking into account the possible presence of an oxide component we determine the intrinsic valence of Yb in YbAuIn to be ~ 2.17. Within the accuracy of the EXAFS technique the Yb3AuGe21n3 sample did not show any noticable oxide component. We estimate the uncertainty in the absolute valence to be ~ 5%, arising mainly from correlations between parameters used to represent the edge-step and white line resonances. The Yb3+ fraction for Yb3AuGezln3 is consistent with that estimated independently from the magnetic measurements described above. 1.6 - .3 N j Absorption (a. u.) 0 00 —-— YbAuIn 300K ----- Yb3AuGe21n3 295K .0 A I 0 8920 8930 8940 8950 8960 8970 Energy (eV) Figure 4-25. Lm absorption edge spectra of Yb in Yb3AuGe21n3 at 295 K (dashed line) and in YbAuIn at 300 K (solid line). 152 Magnetotransport measurements: The Yb3AuGe2In3 compound is clearly metallic. The temperature variation of the electrical resistivity p(T) of Yb3AuGe21n3 between 2.48 and 302.3 K is presented in Figure 4-26. The resistivity data measured on single crystals along the c-axis and at zero applied field reveal metallic conductivity with a room temperature resistivity value p(300K) of 39.6 ,uQ cm. When a magnetic field of 6 Tesla was applied the compound showed no magnetoresistance as it can be seen from the inset in Figure 4-26. In the measured temperature range, the resistivity of Yb3AuGe2In3 can be well described by the Bloch — Grfineisen — Mott formula:9| pm: ,06i0+4RQD[ 0T —KT3 (1) [:0 (ex ~1)(1- cue—x) where po is the residual resistivity, the second term represents electron-phonon scattering, and the third term accounts for Mott’s s-d interband electron scattering. The least-squares fitting procedure of (1) yielded the parameters p0 = 29.08 ,uQ cm and a Debye temperature 90 = 166 K, which is in good agreement with the 09 value that was estimated from the specific heat results (see below). The relatively low 09 is consistent with the presence of heavy atoms in the structure and suggests a soft lattice. 153 33- . A 36)- 4 E O c: 34- . - . . 3 .-‘H=6T//c Q0 -*H=0T 32 30.5 ' II 29.5 _ 30 - 28'50 ' 40 L 80 0 50 100 150 200 250 300 350 Temperature (K) I L I I I 28 Figure 4-26. Temperature variation of the electrical resistivity p0) of Yb3AuGe21n3 from 2.48 to 302.3 K. The dashed line is a fit of the experimental data (squares) to the Bloch — Grfineisen - Mott formula (2). The inset displays the p(T) data for zero applied field (empty squares) and for 6 T applied field (solid trigons) for T < 100 K. The temperature dependent data of the electrical resistivity p(T) of YbAuIn measured between 4.2 and 274.3 K and at zero applied field, are given in Figure 4-27. The resistivity data measured on crystals along the c-axis reveal a rather moderate metallic behavior with resistivity value p(274.3K) of ~ 433 #0 cm. Attempts to describe the p(T) data of YbAuIn with the Bloch — Grfineisen — Mott formula (1) did not result in a successful fit, in contrast with the Yb3AuGezln3. An extra term to the formula perhaps could be required to achieve a good description of the resistivity data for YbAuIn. 154 450 400 - 350 . E 300 - 0 C: 250 . 3 of 200 , 150 100 50 I I I I I 0 50 100 150 200 250 300 Temperature (K) Figure 4-27. Temperature variation of the electrical resistivity p(T) of YbAuIn from 4.2 to 274.3 K and at zero applied field. The temperature dependence of the thermoelectric power (TEP) of Yb3'AuGe21n3 was measured in the temperature range of 310 -— 700 K, Figure 4-28. During the whole temperature range TEP has negative value with a magnitude of -3 ,uV / K at room temperature (310 K). The negative sign of thermopower, is suggestive of the intermediate valence state of the Yb atoms in Yb3AuGezln3 and agrees with the negative TEP observed in most of the Yb—containing mixed- or intermediate-valent compounds as in YbCuGa92 and YbNi4Si93 for example. 155 o”. A ’1 ' o , 4 g -2 ...o ’ ..o.’ .- > 0’ o 3 -3 3 .’ '° ° - m 0 . y a; 4 _ .r . . . g . 0’0: : - O - E 5 l' §€9.0.’.. a) -6 _ . 09.0 _ ..r: . o o i-‘ 0.9.. -7 . ... . 300 400 500 600 700 800 Temperature (K) Figure 4-28. The temperature dependence of the thermoelectric power (TEP) of Yb3AuGe21n3 measured in the temperature range of 310 — 700 K Heat Capacity Measurements: The temperature dependent specific heat from 1.8 to 50 K for ngAuGezln3 is shown in Figure 4-29. The data can be described well by a Debye function (2) where the first and second term correspond to the electronic and the phonon contribution, respectively. N is the number of the atoms in the formula unit and x = hw/kg T. ' 3 90 4 i] T x dx ’KT3 (2) Cp(T)=;/T+ 9M[QD (ex—DZ A fit to the experimental points resulted in a Debye temperature 00 of about 178 K, and an electronic specific heat coefficient 7 z 31 mJ / mol K2, which was determined 156 from y(= Cp / T)T._.o at low temperatures. Therefore the compound does not appear to be a heavy-fermion material according to the arbitrary classification of these compounds into “light”, “moderate” and classical heavy-fermions with 7values lying in the range of ~ 50-60, 100-400 and > 400 ml / mol K2 respectively. Nevertheless, this value of electronic specific heat compares well with the ones found in other mixed valent or intermediate compounds such as the YbAlz,94 YbAl3,95 YngCu4,3O YbNi4Si,93 and YbInAuz96 in which yranges at 15 — 62 mJ / mol K2. C (mJ / mol K) 0) ES. “ 410‘ - - 2104 - a 0 4’ '1' I I I I 0 10 20 30 40 50 Temperature (K) Figure 4-29. Heat capacity (Cp) of Yb3AuGe21n3 measured from 1.8 to 50.3K. The experimental data (circles) are fitted with Debye formula (2) (solid line). 157 The temperature dependent specific heat data measured at a temperature range of 1.8 to 50 K for YbAuIn are shown in Figure 4-30. The data can be also described well by the Debye function (2). A least-square fit to the experimental points resulted in a Debye temperature 09 of about 156 K, and an electronic specific heat coefficient 7 z 84 m] / mol K2, which was determined from 7 (= Cp / T)T_,o at low temperatures. According to the arbitrary classification of the heavy-fermion compounds mentioned above, YbAuIn could be classified as “light” heavy-fermion material. 5104 . r . . . 4104 - 4 £2 E; 310‘ - 4 E 2 ‘104 l- " DO. 110“ - .- 0 l I I I I 0 10 20 30 40 50 Temperature (K) Figure 4-30. Heat capacity (Cp) of YbAuIn measured from 1.8 to 50.3K. The experimental data (circles) are fitted with Debye formula (2) (solid line). 158 4-4. Conclusions Single-crystals of the new Yb based quaternary compound, namely Yb3AuGe21n3 were grown using an excess of indium as a flux. The flux seems necessary to stabilize this compound since direct combination reactions failed to produce the new phase. Yb3AuGe21n3 forms in the hexagonal space group P-62m as an ordered variant of the YbAuIn structure. YbAuIn was also synthesized for comparison of the structure and measured properties. A modified Curie—Weiss fit to the magnetic susceptibility data gave an estimated effective moment of 0.52 713 which is ~ 11% of the value expected for the free-ion Yb”, 4.54 #3. This indicates that the compound contains both Yb2+ and Yb3+ atoms. In order to clarify this XANES studies were also performed which resulted in 85.2% of Yb2+ and 14.8% of Yb3+ leading to an average Yb valence of 2.15. The unique crystallographic Yb site in the structure suggests two hypotheses in which Yb3AuGezln3 could be an (IV) compound with all Yb atoms having a non-integer valence or that the material is a heterogeneous (MV) compound, in which the Yb atoms alternate between 2+ and 3+ state in various unit cells in the lattice. As already stated above, magnetic measurements on various types of samples for both compounds, exhibited significant dependence on the form of the measured sample and other experimental conditions. Random or oriented-single crystals samples and samples ground in open air or inside a glove-box, differ remarkably in their magnetic response and vary from being paramagnetic to exhibit ferromagnetic ordering. The intriguing magnetic properties observed for the two compounds are not yet fully understood, although two possible explanations have been suggested. Future work with additional experimental techniques such as neutron diffraction experiments and detailed magnetic measurements under 159 pressure, are required to further elucidate the reason behind these properties. Nevertheless, our magnetotransport measurements revealed a metallic nature of the compound and negative thermopower which is a common feature of mixed valence Yb compounds. Finally, the heat capacity measurements excluded a heavy-fermion behavior of the material. 160 References: (1) Villars, F.; Calvert, L. D. "Pearson's Handbook of Crystallographic Data for Intermetallic Phases ", 2nd ed. ,' American Society for Metals OH 44073, 1991. (2) Kalychak, Ya. M. J. Alloys Compd. 1997, 341, 262. (3) Szytoula, A.; Leciejewicz, J. "Handbook of Crystal Structures and Magnetic Properties of Rare Earth Intermetallics"; CRC Press: Boca Raton, F l, 1994. (4) Rossi, D.; Ferro, R.; Contardi, V.; Marazza, R. Zeitschrift fixer Metallkunde 1977, 68, 493. (5) Fujii, H.; Uwatoko, Y.; Akayam, M.; Satch, K.; Maeno, Y.; Fujita, T.; Sakurai, J.; Kamimura, H.; Okamoto, T. Jpn. J. Appl. Phys. 1987, 26, 549. (6) Szytula, A.; Penc, B.; Gondek, L. Acta Physica Polonica A 2007, 111, 475. (7) Gondek, L.; Szytula, A.; Penc, 3.; al, et J. Magn. Magn. Mater. 2003, 262, LlXX. (8) Gondek, L; Penc, B.; Szytula, A.; al., et Acta Physica Polonica B 2003, 34, 1209. (9) Mullmann, R.; Mosel, B. D.; Eckert, H.; Kotzyba, G.; Pottgen, R. J. Solid State Chem. 1998, 137, I74. (10) Szytula, A.; Bazela, W.; Gondek, L.; Jaworska-Golab, T.; Penc, B.; Stusser, N.; Zygmunt, A. J. Alloys Compd. 2002, 336, ll. (1 l) Zell, W.; Pott, R.; Roden, B.; Wohlleben, D. Solid State Commun. 1981, 40, 751. (12) Bauchspiess, K. R.; Boksch, W.; Holland-Moritz, E.; Launois, H.; Pott, R.; Wohlleben, D. Proc. Int. Conf on Valence Fluctuations in Solids, St. Barbara, USA. 1981. (13) Pottgen, R. J. Mater. Chem 1996, 6, 63. (14) Oesterreicher, H.; Parker, F. T. Phys. Rev. B 1977, I6, 5009. 161 (15) Fuse, A.; Nakamoto, G.; lshimatsu, N.; Kurisu, M. J. Appl. Phys. 2006, 100, 043712 (16) M. J. Besnus, J. P. Kappler, A. Meyer, .1. Sereni, E. Siaud, R. Lahiouel and .1. Pierre J. Physica B, C 1985 130B. (17) Besnus, M. J.; al, et .1. Less-Common Met. 1986, 120, 101. (18) Kurisu, M.; Fuse, A.; Nobata, T.; Nakamoto, G. Physica B 2000, 281 & 282, 147. (19) Muller, D.; Hussain, S.; Cattaneo, E.; Schneider, H.; Schlabitz, W.; Wohlleben, D. "Valence Instabilities" edited by P. Wachter and H. Boppart (North-Holland), Amsterdam, 1982, 463. (20) Pottgen, R. Z. Naturforch B .' Chem. Sci 1994, 49B, 1525. (21) M. Giovannini, E. Bauer, H. Michor, G. Hilscher, A. Galatanu, A. Saccone and P. Rogl Intermetallics 2001, 9. (22) ANDRE G, BAZELA W, OLES A, SZYTULA A JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1992, 109. (23) Felner, 1.; Nowik, 1. Phys. Rev. B 1986, 33, 617. (24) Felner, 1.; Nowik, I.; Vaknin, D.; Potzel, U.; Moser, J.; Kalvius, G. M.; Wortmann, G., Schmiester, G.; Hilscher, G., Gratz, E.; Schmitzer, C.; Pillmayr, N.; Prasad, K. G., Waard, H. de; Pinto, H. Phys. Rev. B 1987, 35, 6956. (25) Nowik, 1.; Felner, I.; Voiron, J.; Beille, J.; Najib, A.; Lachiesserie, E. du Temolet de; Gratz, E. Phys. Rev. B 1988, 37, 5633. (26) Sarrao, J. L. Physica B 1999, 259-261, 128. (27) Sarrao, J. L.; lmmer, C. D.; Fisk, Z.; Booth, C. H.; Figueroa, E.; Lawrence, J. M.; Modler, R.; Cornelius, A. L.; Hundley, M. F.; Kwei, G. H.; Thompson, J. D. Phys. Rev. B 1999, 59, 6855. (28) Mushnikov, N. V.; Goto, T.; Rozenfeld, E. V.; Yoshimura, K.; Zhang, W.; Yamada, M.; Kageyama, H. J. Phys. .' Condens. Matter 2003, 15, 2811. 162 (29) Junhui, H.E.; Tsujii, N.; Yoshimura, K.; Kosuge, K.; Goto, T. J. Phys. Soc. Jpn 1997, 66, 2481. (30) Golubkov, A. V.; Parfen'eva, L. S.; Smimov, 1. A.; Misiorek, H.; Mucha, J. Physics of the Solid State 2007, 49, 2038-2041. (31) Hoffmann, R.-D.; Pottgen, R.; Rosenhahn, C.; Mosel, B. D.; Kunnen, B.; Kotzyba, G. J. Solid Sate Chem. 1999, 145, 283. (32) Galadzhun, Y. V.; Hoffmann, R.-D.; Pottgen, R.; Adam, M. J. Solid Sate Chem. 1999, I48, 425 (33) Salvador, J. R.; Hoang, K.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2007, 46, 6933 (34) Hoffmann, R. D.; Pottgen, R.; Zaremba, V. 1.; Kalychak, Y. M. Z. Naturforch B .' Chem. Sci 2000, 55, 834. (35) Kanatzidis, M. G.; Pottgen, R.; Jeitschko, W. Angewandte Chemie-International Edition 2005, 44, 6996-7023. (36) Canfield, P. C.; Fisk, Z. Z. Philos. Mag. B 1992, 65, 11 17-1123. (37) Bud'ko, S. 1.; Islam, Z.; Wiener, T. A.; Fisher, 1. R.; Lacerda, A. H.; Canfield, P. C. J. Magn. Magn. Mater. 1999, 205, 53-78. (38) Fisher, 1. R.; Islam, 2.; Canfield, P. C. J. Magn. Magn. Mater. 1999, 202, 1-10. (39) Nicklas, M.; Sidorov, V. A.; Borges, H. A.; Pagliuso, P. G.; Petrovic, C.; Fisk, Z.; Sarrao, J. L.; Thompson, and J. D. Physical Review B 2004, 67, 020506. (40) Hundley, M. F.; Sarrao, J. L.; Thompson, J. D.; Movshovich, R.; Jaime, M.; Petrovic, C.; Fisk, and Z. Phys. Rev. B 2001, 65, 024401. (41) Macaluso, R. T.; Sarrao, J. L.; Moreno, N. 0.; Pagliuso, P.G.; Thompson, J. D.; Fronczek, F. R.; Hundley, M. F .; Malinowski, A.; Chan, J. Y. Chem. Mater. 2003, 15, 1394-1398. 163 (42) Chen, X. Z.; Sportouch, S.; Sieve, B.; Brazis, P.; Kannewurf, C. R.; Cowen, J. A.; Patschke, R.; Kanatzidis, M. G. Chem. Mater. 1998, 10, 3202-321 1. (43) B. Sieve; X. Z. Chen; R. Henning; P. Brazis; C. R. Kannewurf; J. A. Cowen; A. J. Schultz; Kanatzidis, M. G. J. Am. Chem. Soc 2001, 123, 7040. (44) Chen, X. Z.; Larson, P.; Sportouch, S.; Brazis, P.; Mahanti, S. D.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 1999, 11, 75-83. (45) Zhuravleva, M. A.; Kanatzidis, M. G. Z. Naturforch B .' Sec. B 2003, 58, 649-657. (46) Zhuravleva, M. A.; Pcionek, R. J .; Wang, X. P.; Schultz, A. J.; Kanatzidis, M. G. Inorg. Chem. 2003, 42, 6412-6424. (47) Zhuravleva, M. A.; Evain, M.; Petricek, V.; Kanatzidis, M. G. J. Am. Chem. Soc 2007, 129, 3082-3083. (48) Chen, X. 2.; Small, P.; Sportouch, S.; Zhuravleva, M. ; Brazis, P.; Kannewurf, C. R.; Kanatzidis, M. G. Chem. Mater. 2000, 12, 2520-2522. (49) Lattumer, S. E.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2003, 42, 7959- 7966. (50) Wu, X. U.; Lattumer, S. E.; Kanatzidis, M. G. Inorg. Chem. 2006, 45, 5358-5366. (51) Lattumer, S. E.; Kanatzidis, M. G. Inorg. Chem. 2008, 4 7, 2089-2097. (52) Lattumer, S. 13.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Chem. Mater. 2002, 14, 1695-1705. (53) Salvador, J. R.; Gour, J. R.; Bilc, D.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2004, 43, 1403-1410. (54) Salvador, J. R.; Bilc, D.; Gour, J. R.; Mahanti, S. D.; Kanatzidis, M. G. Inorg. Chem. 2005, 44, 8670-8679 (55) Salvador, J. R.; Kanatzidis, M. G. Inorg. Chem. 2006, 45, 7091-7099. 164 (56) Chondroudi, M.; Balasubramanian, M.; Welp, U.; Kwok, W.-K.; Kanatzidis, M. G. Chem. Mater. 2007, 19, 4769-4775. (57) Bailey, M. S.; McCuire, M. A.; DiSalvo, and F. J. J. Solid Sate Chem. 2005, 178, 3494- 3499. (58) Benbow, E. M.; Lattumer, S. E. Inorg. Chem. 2006, 179, 3989-3996. (59) Klunter, W.; Jung, W. J. Solid Sate Chem. 2006, 179, 2880-2888. (60) Zaremba, V. 1.; Dubenskiy, V. P.; Rodewald, U. C.; Heying, B.; Pottgen, R. J. Solid State Chem. 2006, 179, 891-897. mm as, «BA-III. l'-' (61) Lukachuk, M.; Galadzhun, Y. V.; Zaremba, R. 1.; Dzevenko, M. V.; Kalychak, Y. M.; Zaremba, V. 1.; Rodewald, U. C.; Pottgen, R. J. Solid State Chem. 2005, 178, 2724-2733. (62) Macaluso, R. T.; Sarrao, J. L.; Pagliuso, P.G.; Moreno, N. 0.; Goodrich, R. G.; Browne, D. A.; Fronczek, F. R.; Chan, J. Y. J. Solid Sate Chem. 2002, 166, 245-250. (63) Kindler, B.; F insterbusch, D.; Graf, R.; Ritter, F. Phys. Rev. B 1994, 50, 704. (64) Bauer, E. Adv. Phys. 1991, 40, 417. (65) Wachter, P. Handbook on the Physics and Chemistry of Rare Earths 1994, (Elsevier Science, Amsterdam), 177. (66) Lawrence, J. M.; Riseborough, P. S.; Park, R. D. Rep. Progr. Phys. 1981, 44, 1. (67) Fisk, Z.; Hess, D. W.; Pethick, C. J.; Pines, D.; Smith, J. L.; Thomson, J. D.; Willis, J. 0. Science 1988, 239, 33. (68) GmbH, STOE & C16 2006, D 64295 Darmstadt, Germany. (69) Bruker Advanced X-ray Solutions SHELXT L (Version 6.14), Bruker AXS Inc., Madison, WI (2003). (70) Kraft, S.; Stumpel, J .; Becker, P.; Kuetgens, U. Rev. Sci. Instrum. 1996, 6 7, 681. 165 (71) Ravel, B.; Newville, M. J. Synchrotron Rad. 2005, 12:4, 537-541. (72) Li, Qing'An; Gray, K. E.; Mitchell, J. F. Phys. Rev. B 1999, 59, 9357 - 9361. (73) Advanced Heat Capacity with Helium-3 Application Note. Physical Property Measurement System Brochure 1999. (74) Yoshida, M.; Akiba, E.; Shimojo, Y.; Morii, Y.; Izumi, F. J. Alloys Compd. 1995, 231, 755. (75) S. B. Hendricks and P. R. Kosting Z. Krist. 1930, 74, 51 l. (76) Donohue, J. ”The structures of the elements "; Wiley: New York, 1974. (77) Mao, J.-G.; Goodey, J.; Guloy, A.M. Inorg. Chem. 2002, 4], 931-937. (78) Mao, J.-G.; Xu, 2.; Guloy, A.M. Inorg. Chem. 2001, 40, 4472-4477. (79) Nychyporuk, G.;Zaremba, V.;Kalychak, Ya.M.;Stepien-Damm, J .;Pietraszko, A. Journal of Alloys Compd. 2000, 312, 154. (80) Kawamura, H. J. Phys. .' Condens. Matter 1998, 10, 4707-4754. (81) Yoshida, H.; Ahlert, S.; Jansen, M.; Okamoto, Y.; Yamaura, J .-I.; Hiroi, Z. J. Phys. Soc. Jpn 2008, 77, 074719. (82) Ehlers, 0.; Maletta, H. z. Phys. B 1996, 101,317 - 327. (83) Javorsky, P.; Tuan, N.C.; Divis, M.; Havela, L.; Svoboda, P.; Sechovsky, V.; Hilscher, G. J. Magn. Magn. Mater. 1995, 140-144, 1139. (84) Rao, C. N. R.; Sarma, D. D.; Sarode, P. R.; Sampathkumaran, E. V.; Gupta, L. C.; Vijayaraghavan, R. Chemical Physics Letters 1980, 76, 413-415. (85) Hatwar, T. K.; Nayak, R. M.; Padalia, B. D.; Ghatikar, M. N.; Sampathkumaran, E. V.; Gupta, L. C.; Vijayaraghavan, R. Solid State Communications 1980, 34, 617-620. 166 (86) Moreschini, L.; Dallera, C.; Joyce, J. J.; Sarrao, J. L.; Bauer, E. D.; Fritsch, V.; Bobev, S.; Carpene, E.; Huotari, S.; Vanko, G.; Monaco, G.; Lacovig, P.; Panaccione, G.; Fondacaro, A.; Paolicelli, G.; Torelli, P.; Grioni, M. Physical Review B 2007, 75. (87) Johansson, 3.; Rosengren, A. Phys. Rev. B 1975, 1], 2836. (88) Dallera, C.; Wessely, 0.; Colarieti-Tosti, M.; Eriksson, 0.; Ahuja, R.; Johansson, 8.; Katsnelson, M. 1.; Annese, E.; Rueff, J. P.; Vanko, G., Braicovich, L.; Grioni, M. Physical Review B 2006, 74, 4. (89) Lubbers, R.; Dumschat, J.; Wortmann, G.; Bauer, E. J. Phys. IV France 1997, 7, C2- 1021. (90) Dallera, C.; Annese, E.; Rueff, J. P.; Palenzona, A.; Vanko, G.; Braicovich, L.; Shukla, A.; Grioni, M. J. Electron Spectrosc. Relat. Phenom. 2004, I37-40, 651-655. (91) Mott, N. F.; Jones, H. "The Theory of the Properties of Metals and Alloys" Oxford University Press: New York, 195 8; Vol. p. 240. (92) Androja, D. T.; Malik, S. K.; Padalia, B. D.; Bhatia, S. N.; Walia, R.; Vijayaraghvan, R. Phys. Rev. B 1990, 42, 2700. (93) Kowalczyk, A.; Falkowski, M.; Tolinski, T.; Tran, V. H.; Miiller, W.; Reiffers, M.; Timko, M. Materials Research Bulletin 2008, 43, 185. (94) Gorlach, T.; Pfleiderer, C.; Grube, K.; Lohneysen, H.v. Phys. Rev. B 2005, 71, 033101. (95) Klaasse, J. C. P.; Boer, F. R. de; Chatel, P. F. de Phys. B 1981, 106, 178. (96) Tsujii, N.; Yoshimura, K; Kosuge, K. J. Phys. .' Condens. 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