Spin transfer torque driven by interfacial roughness and spin-orbital scattering*

Spin transfer torques allow efficient electric control of magnetization dynamics in nanoscale heterostructures. In this work, we theoretically investigate a spin-transfer torque effect in a ferromagnetic metal layer emanating from surface roughness and Rashba spin-orbit scattering in the presence of an in-plane charge current. A full quantum mechanical approach is used to evaluate the charge-current-spin-current response function, which allows us to analyze the effect of quantum interference between scattering states near the Rashba interface. In the ballistic regime, we find that while a field-like torque can be induced by applying an in-plane current regardless of the surface roughness, a damping-like torque only emerges from a rough Rashba interface whereby the interference between scattering states is partially suppressed.