Spin–orbit torques provide electrical control of magnetization dynamics in nanoscale heterostructures. Interfaces play a crucial role in these torques from creating the transfer of spin current to the magnetization or generating spin currents and spin accumulations. Spin-orbit torques tend to be localized to the interface because spin currents tend not to penetrate deep into ferromagnets unless the spins are aligned with the magnetization. However, describing a spin-orbit torque as interfacial generally implies that the spin-orbit coupling responsible for the torque is at the interface. That such torques might be important should not be a surprise given the importance of interfacial magnetocrystalline anisotropies and Dzyaloshinskii-Moriya interactions. Unfortunately, it can be difficult to differentiate between interfacial spin-orbit torques and those that originate away from the interfaces. There is no difference in the symmetries of the torques. In addition, changes in other properties can complicate the interpretation of thickness-dependent studies. Never-the-less, in looking to optimize spin-orbit torques, it is useful to understand the role of interfaces. In this talk, I describe the mechanisms that give rise to interfacial spin-orbit torques, discuss where they might be important, and speculate on the role they might play in the commercialization of devices based on spin-orbit torques.

References:

V. P. Amin, P. M. Haney, and M. D. Stiles, J. of Appl. Phys. 128, 151101 (2020).
V. P. Amin, J. Zemen, and M. D. Stiles, Phys. Rev. Lett. 121, 136805 (2018).
V. P. Amin and M. D. Stiles, Phys. Rev. B 94, 104420 (2016).
V. P. Amin and M. D. Stiles, Phys. Rev. B 94, 104419 (2016).