Interfacial spin transmission and spin-orbit torques in as-grown and annealed W/Co2FeAl/MgO multilayers

Abstract

The interfacial spin transmission and spin-orbit torques (SOTs) in as-grown and annealed W/Co2FeAl(CFA)/MgO multilayers are studied by the spin-torque ferromagnetic resonance (ST-FMR) technique. The effective spin-mixing conductance of 4.40 × 10 14 ω - 1 m - 2 and the interfacial spin transparency Tin of 0.47 are obtained for the as-grown samples, which are comparable to those of the widely employed W/CoFeB bilayer. The annealing influence on the W/CFA/MgO multilayer is subsequently studied. The damping-like torque efficiency (ζDL) and field-like torque efficiency (ζFL) are extracted for different annealing temperatures via modulation of damping measurements and the angular dependence of ST-FMR spectra. Importantly, the ζDL value is fairly large (0.3 -0.5) and does not degrade even when the annealing temperature is increased up to 420 °C. Our results indicate that the studied W/CFA/MgO multilayers could be promising candidate materials for designing and developing SOT-driven spintronic devices.