Investigating the influence of the depinning energy barrier on domain wall motion in perpendicularly magnetized Pt/Co/Cr/Ta multilayers

摘要

Domain wall (DW) motion via current induced spin-orbit torque (SOT) and/or a magnetic field in ferromagnet/heavy metal heterostructure has attracted abundant interests due to its potential applications in magnetic memories and logic devices. In this work, we study the influence of the depinning energy barrier on DW motion in the creep regime using the polar magneto-optical Kerr microscopy in the Cr layer decorated Pt/Co/Ta structure. We find that although the SOT efficiency shows a significant enhancement in the Pt/Co/Cr/Ta system, but the current-induced DW motion efficiency still shows an attenuation. We confirm that this unexpected result is caused by the enhanced pinning energy barrier, extracted from the relationship between the cumulative depinning probability (P-d) and the depinning time (t). Moreover, the relationship between P-d and t exhibits preferred exponential distribution, indicating that a single energy barrier governs the depinning behavior in our systems. We also reveal that the energy barrier depends on the interface between the ferromagnet and heavy metal. Our study suggests that the current-induced DW motion efficiency is not only determined by the SOT efficiency, but also the depinning energy barrier.