Domain wall depinning analysis on spin-orbit torque switching in perpendicularly magnetized devices

Wei-Bang Liao^1*, Chun-Yi Lin¹, Tung-Yue Cheng¹, Chao-Chung Huang¹, Tian-Yue Chen¹, Chi-Feng Pai¹

¹Materials Science and Engineering, National Taiwan University, Taiwan

* Presenter:Wei-Bang Liao, email:f07527093@ntu.edu.tw

Spin-orbit torque (SOT)-induced magnetization switching can be described by either macrospin coherent switching or domain-wall dynamics scenario, depending on the scale of the device. In this work, we systematically scrutinize the processing effect and SOT properties from 5-μm Hall bars to submicrometer-sized pillars and magnetic tunnel junctions (MTJs), with an identical W-based magnetic heterostructures. We first examine that coercivity enhances when reducing the pillar size. Next, the damping-like SOT efficiency is characterized to be size independent through the current-driven hysteresis loop shift measurement. On the contrary, critical switching current density in SOT switching measurement increases when scaling down the pillar size, suggesting the strong correlation between coercivity and critical switching current density. Furthermore, both loop shift phase diagram and domain depinning model provide consistent estimation of critical switching current density. Last, we compare the SOT switching results from a micrometer-sized Hall bar device and a micrometer-sized three-terminal MTJ device with identical magnetic heterostructures, where a consistent estimated SOT efficiency can be obtained. Our results give insight into the processing and size effects on magnetic devices and provide proper protocols for SOT efficiency and critical switching current density estimations.

Keywords: spin-orbit torque, spin Hall effect, domain wall depinning, magnetic tunnel junction