Spin transfer torque in current-perpendicular-to-plane multilayer structure induced by spin relaxation in the capping layer

Abstract

We study the effect of spin relaxation (SR) in the capping layer on spin-injection (SI) efficiency and spin torque (Γ) in a current-perpendicular-to-plane multilayer device comprising fixed(FM1)-spacer(NM1)-free(FM2)-capping(NM2) layers. In spin transfer switching of spin valves, high SI into free layer increases the net spin flux in the free layer and thus induces high Γ for magnetization switching. Our results show that the effect of capping layer SR on SI and Γ depends on the FM1 thickness (dFM1). The relationship between SR, SI, and dFM1 is explained by analyzing the spatial variation of spin accumulation across the device. The results of our calculations provide the theoretical basis for enhancing (minimizing) Γ by the localized manipulation of SR within the capping layer for magnetic random access memory (sensor) applications.