Field-like and Damping-like Spin-Orbit Torque Efficiencies at an Interface Between NiFe and Bi₂Se₃

An electrical current driven through a topological insulator can simultaneously induce a field-like spin-orbit torque (SOT) and a damping-like SOT in a proximitized ferromagnetic layer. Depending on the magnetic anisotropy, the field-like or damping-like SOT may further lead to an in-plane or out-of-plane magnetization reversal in the ferromagnetic layer. Therefore, it is an important aspect to determine the efficiencies of the two SOTs in order to realize magnetization manipulation in a ferromagnet/topological-insulator bilayer structure. In this work, we systematically studied the second harmonic Hall effect, magnetoresistance, ferromagnetic resonance of a NiFe/Bi₂Se₃ sample. Taking the current shunting effect due to the metallic ferromagnetic layer into account, we obtained a field-like SOT efficiency of ~ 0.38 and a damping-like SOT of ~ 0.06 for the bilayer structure.