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 (SOT) devices based on their ability to generate spin-polarized current and exchange bias when combined with FMs [1]. Since the exchange bias of the AFM/FM bilayer appeared to be tailorable by SOT [1-2], it opens a great opportunity for AFM-based spintronics technology that the SOT can modify the spin texture of AFM and FM can serve for detection. In this talk, several AFM/FM systems will be demonstrated for studying the interfacial dynamics of AFM spins. 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 [2].
Keywords – spin-orbit torque, antiferromagnet, ratchet, exchange bias.
References:
[1] P. H. Lin et al. Nature Materials 18, 335 (2019).
[2] C. Y. Yang et al. Applied Physics Letters 118, 102403 (2021).
[3] Y. H. Huang et al. Advanced Functional Materials 32, 2111653 (2022).