Evaluation of spin-orbit torque in a L1 0 -FePt single layer and a L1 0 -FePt / Pt bilayer

We investigated the spin-orbit torque (SOT) in a L1(0)-FePt single layer and a L1(0)-FePt/Pt bilayer by measuring the harmonic Hall voltages, where the L1(0)-FePt layers exhibited perpendicular magnetization. The harmonic signals for the L1(0)-FePt single layer did not depend on applied electric voltage, suggesting the negligible self-induced SOT in the FePt. In the case of a L1(0)-FePt/Pt bilayer, on the other hand, SOT from the Pt layer exerted on the FePt magnetization. We found that the longitudinal effective field is dominant whereas the transverse effective field is significantly small for the present L1(0)-FePt/Pt bilayer. (C) 2019 The Japan Society of Applied Physics