We report on structural, magnetic, transport, and spin-polarization measurements of the Heusler alloys Co 2 MnSi and NiMnSb. Laue diffraction patterns confirm the single-crystal nature of Co 2 MnSi. Roomtemperature transport measurements show a negative magnetoresistance in NiMnSb. Point-contact Andreev reflection measurements of the spin polarization yield polarization values for Co 2 MnSi and NiMnSb of 56% and 45%, respectively. Temperature dependence of resistivity for Co 2 MnSi reveals a relatively large residual resistivity ratio ( 293 K / 5 K ) typical of single-crystal Heusler alloys. In NiMnSb, resistivity and magnetization as a function of temperature show evidence of a magnetic phase transition near 90 K.

We observe a strong correlation between magnetization relaxation and electrical resistivity in thin Permalloy (Ni81Fe19, "Py") films. Electron scattering rates in the films were affected by varying film thickness and deposition conditions. This shows that the magnetization relaxation mechanism is analogous to "bulk" relaxation, where phonon scattering in bulk is replaced by surface and defect scattering in thin films. Another interesting finding is the increased magnetization damping with Pt layers adjacent to the Py films. This is attributed to the strong spin-orbit coupling in Pt, resulting in spin-flip scattering of electrons that enter from the Py.

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