Spin-orbit torque magnetometry for as-prepared films by wide-field magneto-optical Kerr effect*

Magneto-optical Kerr effect (MOKE) is an efficient tool to probe surface magnetization in thin film samples. Here we present a wide-field MOKE technique that adopts a Köhler illumination scheme to characterize the current-induced spin-orbit torques (SOTs) in micron-sized and more importantly, unpatterned/as-prepared magnetic heterostructures with perpendicular magnetic anisotropy. Through a current-induced hysteresis loop shift analysis, we quantify the SOT efficiency of both patterned and unpatterned Ta-based heterostructures to be ~-0.08, which is fairly close to previously reported values obtained by various electrical means. The proposed wide-field MOKE approach therefore provides an instant and direct characterization of SOT, without the need of any further processing on the as-prepared film stacks and further interpretation on the measured signals.