Determination of spin torque efficiencies in heterostructures with perpendicular magnetic anisotropy

Current-induced spin-orbit torque (SOT) in magnetic heterostructures with perpendicular magnetic anisotropy is an efficient mechanism to control the magnetic moments therein. The authors present a Hall-voltage-based technique that allows them to simultaneously determine two key physical quantities describing SOT in magnetic heterostructures: the SOT efficiency and the magnitude of effective Dzyaloshinskii-Moriya interaction field. With the help of this new technique, the authors find that the spin-orbit torque, apart from the conventional spin-Hall-induced contribution, includes another geometrical component that depends on the shape of the ferromagnetic layer of the heterostructure. This opens a possibility for engineering SOT switching without any aid of external magnetic field, with possible applications for magnetic random access memory applications.