Phenomenology of current-induced spin-orbit torques

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 Pt vertical bar Co vertical bar AlOx, 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 nonrelativistic 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.