Spin-Orbit Torques

A series of fundamental discoveries over the past thirty years has dramatically improved our ability to read, write, and process magnetically stored information. I will briefly review some of these advances before focusing on the recently discovered spin-orbit torques, which act on the collective spin of thin film ferromagnets when they are placed on a substrate with strong spin-orbit interactions and are particularly promising for applications. Spin-orbit-torques are normally interpreted in terms of the spin Hall effect, spin-current that flows perpendicular to charge current in any conductor, but there is little direct evidence for this interpretation. I will discuss a theory of spin-orbit torques that focuses on the role of current-induced spin-densities and apply it to magnetically doped topological insulator thin films, which I will argue provide an ideal test for spin-orbit torque theories.