Direct detection of spin-orbit effective fields through magneto-optical Kerr effect

Current-induced effective magnetic fields provide efficient methods to electrically control the magnetization switching in ultrathin magnetic films. It is getting clearer that the two terms of spin-orbit torque (SOT), i.e., the dampinglike SOT and the fieldlike SOT, play different roles during the magnetization switching process. Fast and direct estimation of both effective fields are crucial for highly efficient magnetization switching. Methods to extract the amplitudes of the effective fields have been intensively investigated, but they are either complex or require multiparameter fitting, especially for the fieldlike field. We introduce the direct detection of SOT effective fields using hysteresis-loop shift through the magneto-optical Kerr effect in the out-of-plane Pt/Co/W and in-plane Pt/Fe/MgO trilayer systems. The results show strong agreement with transport measurements. Benefiting from noncontact optical detection, our approach in the detection of the spin-orbit effective field has great advantages in the simplified device fabrication processing, and it is suitable not only for metallic systems but also for insulating systems, which paves the way to direct detection of SOT effective fields.