A Spin-Orbit Torque Ratchet at Ferromagnet/Antiferromagnet Interface via Exchange Spring

Yu Han Huang, Chao Yao Yang*, Chih Wei Cheng, Albert Lee, Chih Hsiang Tseng, Hao Wu, Quanjun Pan, Xiaoyu Che, Chih Huang Lai, Kang Lang Wang, Hong Ji Lin, Yuan Chieh Tseng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The antiferromagnet (AFM) and ferromagnet (FM) interface is a unique branch of magnetics of broad scientific interest. AFMs play an important role in spin-orbit torque devices based on their ability to generate spin-polarized current and exchange bias when combined with FMs. In this study, an interesting spin-orbit torque (SOT) ratchet involving the exchange spring effect in an IrMn/CoFeB bilayer device with perpendicular anisotropy and exchange bias is developed. The combined use of electrical and spectroscopic analysis reveals that the exchange spring in IrMn/CoFeB bilayer yields unidirectional anisotropy, resulting in a collinear/orthogonal AFM/FM spin configuration at the interface upon switching CoFeB magnetization upward/downward. The ratcheting characteristics resulting from unidirectional anisotropy manifest in SOT switching. In this process, magnetization against the exchange spring features digital-like switching with a sharp transition, whereas the reverse function is characteristic of analog switching with a gradual transition tail. The dual digital-analog characteristics of the IrMn/CoFeB bilayer may be of benefit in neuromorphic and memory applications.

Original languageEnglish
JournalAdvanced Functional Materials
DOIs
StateAccepted/In press - 2022

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