INVESTIGATING SPIN-ORBIT TORQUES IN A CO/PT BILAYER USING FIRST PRINCIPLES CALCULATIONS

Abstract

The spin-orbit torque in a disordered Co/Pt bilayer is estimated using a non-equilibrium Green's function formalism. The torque has two formal components: Fermi-surface and Fermi-sea contributions. The Fermi-surface component dominates at low temperatures, while the Fermi-sea term is substantial at normal temperatures. In addition to the typical field-like and damping effects, the odd torque has a considerable planar Hall-like component (m E)m (z m), which contributes to damping. While field-like torques on Pt atoms do not require spin-orbit coupling, it is primarily responsible for torques that contribute to damping.