Two simple tests for models of current-induced magnetization switching

We describe two simple tests for models of current-induced magnetization switching due to spin-transfer torque in ferromagnetic/nonmagnetic/ferromagnetic (F/N/F) trilayers. The first involves comparing calculated and measured values of the ratio X=Delta I(Cu)/Delta I(CuGe), where Delta I=I+-I-, the difference between switching currents for + and - current directions, when only the N-layer is changed from Cu to a dilute CuGe alloy. The Ge in Cu causes a large increase in elastic scattering (large reduction in mean-free path), but only a smaller increase in spin-orbit scattering (leaving the spin-diffusion length still relatively long). The second involves comparing calculated and measured values of the ratios (I+/I-) for both Cu and CuGe. Unexpectedly, the most sophisticated models generally fit the first ratio least well at both 295 and 4.2 K. None of the models agree with the ratio (I+/I-). (c) 2008 American Institute of Physics.