Interface enhanced spin-orbit torques and current-induced magnetization switching of Pd/Co/AlO${}_x$ layers

Abstract

Magnetic heterostructures that combine large spin-orbit torque efficiency, perpendicular magnetic anisotropy, and low resistivity are key to develop electrically-controlled memory and logic devices. Here we report on vector measurements of the current-induced spin orbit torques and magnetization switching in perpendicularly magnetized Pd/Co/AlO${}_x$ layers as a function of Pd thickness. We find sizeable damping-like (DL) and field-like (FL) torques, of the order of 1~mT per $10^7$~A/cm${}^2$, which have different thickness and magnetization angle dependence. The analysis of the DL torque efficiency per unit current density and electric field using drift-diffusion theory leads to an effective spin Hall angle and spin diffusion length of Pd larger than 0.03 and 7~nm, respectively. The FL SOT includes a significant interface contribution, is larger than estimated using drift-diffusion parameters, and is further strongly enhanced upon rotation of the magnetization from the out-of-plane to the in-plane direction. Finally, taking advantage of the large spin-orbit torques in this system, we demonstrate bipolar magnetization switching of Pd/Co/AlO${}_x$ layers with similar current density as used for Pt/Co layers with comparable perpendicular magnetic anisotropy.

References in corpus (4)

• Theory of spin Hall magnetoresistance
• Angular and temperature dependence of current induced spin-orbit effective fields in Ta/CoFeB/MgO nanowires
• Angular dependence of spin-orbit spin transfer torques
• Direct Method for Calculating Temperature-Dependent Transport Properties

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