We describe two simple tests for models of current-induced magnetization switching due to spin-transfer-torque in ferromagnetic/non-magnetic/ferromagnetic (F/N/F) trilayers. The first involves comparing calculated and measured values of the ratio X = ?I(Cu)/?I(CuGe), where ?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 K and 4.2 K. None of the models agree with the ratio (I+/I- ).
Citation: Journal of Applied Physics
Pub Type: Journals