Phenomenology of Current-Induced Spin-Orbit Torques

TL;DR

This paper introduces a new phenomenological model for current-induced spin-orbit torques applicable across different material systems, revealing a relativistic dissipative torque that influences domain wall motion.

Contribution

It presents a novel phenomenology of spin-orbit torques valid for any intrinsic spin-orbit coupling strength, including the discovery of a relativistic dissipative torque affecting domain walls.

Findings

Domain walls respond to a new relativistic dissipative torque.

The torque depends on domain wall structure and Dzyaloshinskii-Moriya interaction.

Electric currents can move domain walls via combined torques.

Abstract

Currents induce magnetization torques via spin-transfer when the spin angular momentum is conserved or via relativistic spin-orbit coupling. Beyond simple models, the relationship between material properties and spin-orbit torques is not known. Here, we present a novel phenomenology of current-induced torques that is valid for any strength of intrinsic spin-orbit coupling. In $\rm Pt|Co|AlO_x$, we demonstrate that the domain walls move in response to a novel relativistic dissipative torque that is dependent on the domain wall structure and that can be controlled via the Dzyaloshinskii-Moriya interaction. Unlike the non-relativistic spin-transfer torque, the new torque can, together with the spin-Hall effect in the Pt-layer, move domain walls by means of electric currents parallel to the walls.