Anomalous spin-orbit torque switching due to field-like torque-assisted domain wall reflection

TL;DR

This paper reveals that field-like torque significantly influences spin-orbit torque switching by causing domain wall reflections at edges, leading to unexpected decreases in switching probability at longer pulse durations.

Contribution

It demonstrates the crucial role of field-like torque in SOT switching and highlights the impact of torque sign correlation on domain wall dynamics, supported by time-resolved measurements and micromagnetic analysis.

Findings

Decreased switching probability at longer pulse widths.

Domain wall reflections depend on field-like torque.

Sign of field-like torque affects switching efficiency.

Abstract

Spin-orbit torques (SOT) allow the electrical control of magnetic states. Current-induced SOT switching of the perpendicular magnetization is of particular technological importance. The SOT consists of damping-like and field-like torques so that the efficient SOT switching requires to understand combined effects of the two torque-components. Previous quasi-static measurements have reported an increased switching probability with the width of current pulses, as predicted with considering the damping-like torque only. Here we report a decreased switching probability at longer pulse-widths, based on time-resolved measurements. Micromagnetic analysis reveals that this anomalous SOT switching results from domain wall reflections at sample edges. The domain wall reflection is found to strongly depend on the field-like torque and its relative sign to the damping-like torque. Our result demonstrates a key role of the field-like torque in the deterministic SOT switching and notifies the importance of sign correlation of the two torque-components, which may shed light on the SOT switching mechanism.