This thesis consists of three studies of Current-Perpendicular-to-the-Planes (CPP) Magnetoresistance (MR) of sputtered ferromagnetic/non-magnetic (F/N) multilayers. (a) The firststudy involves a double-blind comparison of our measurements of the interface specic resistance AR (area A through which the CPP current flows times the CPP resistance R) of Pd/Ir interfaces with no-free-parameter calculations. (b) The second study is of spin relaxation within the antiferromagnets (AF) IrMn and FeMn and at their interfaces with Cu. (c) The third study is of the MR of multilayers involving a nominal half-metal Heusler alloy, Co2Fe(Al0.5Si0.5) (CFAS). A true half-metal should give an especially large CPP-MR. This study involves a different sample geometry, combining optical lithography and ion-beam etching, with epitaxial sputtering at elevated temperatures.(a) For four pairs of lattice-matched metals (Ag/Au, Co/Cu, Fe/Cr, and Pt/Pd) having the same crystal structure and the same lattice parameter to within 1%, no-free-parameter calculations of 2AR, twice the interface specic resistance AR have agreed with measuredvalues to within mutual uncertainties. For three pairs, the measured values were known when the calculations were made. For the fourth pair, Pt/Pd, they were not. In contrast, calculations for non-matched pairs, where the lattice parameters diered by 5% or more, disagreedwith measured values. In this thesis we study a fth pair, Pd and Ir, where the lattice parameter mismatch is intermediate, 1.3%. The project was done double-blind with theory collaborators Wang and Xia, with experiment and calculations shared only after both groupssettled on their separate values. The values for Pd/Ir calculated with the same assumptions used previously were just outside of uncertainty of the measured ones. An improved calculationgave agreement between the two values.(b) Antiferromagnets (AFs) play important roles in CPP-MR devices as sources of pinning for F-layers in exchange-biased spin-valves (EBSVs), and are also part of a burgeoning field of AF spintronics. For both structures, it is important to understand spin-relaxationwithin sputtered AFs and at AF/N interfaces. A prior study of spin-relaxation in sputtered FeMn found strong spin-flipping at FeMn/Cu interfaces, but was unable to determine the size of spin-flipping within the FeMn itself. In this thesis we find strong spin-flipping atIrMn/Cu interfaces and conrm strong spin-flipping at FeMn/Cu interfaces. We also discovered an interesting new phenomenon, a weak magnetic dependence of AR in Py, that makes us unable to put a tight bound on the bulk spin-diusion lengths in sputtered IrMnor FeMn. But these lengths are probably short.(c) The CPP-MR of an F/N multilayer will be enhanced by an F-metal with high spin scattering asymmetry, making such a multilayer more competitive for devices. Half-metallic ferromagnetic metals, such as Heusler alloys, are predicted to have high asymmetry. Experimentswith the Heusler alloy CFAS have shown both large Tunneling Magnetoresistance (TMR) and large CPP-MR for multilayers with non-superconducting electrodes sputtered at room temperature and then post-annealed to 5000C. In this thesis we attempt to optimize epitaxial growth using high temperature sputtering to produce highly ordered Heusler alloys grown on superconducting electrodes. We are able to grow CFAS epitaxially, but have obtained maximum CPP MR only about one-third (40%) as large as we expected.
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