Large exchange bias enhancement and control of ferromagnetic energy landscape by solid-state hydrogen gating

M Usama Hasan; Alexander E Kossak; Geoffrey S D Beach

doi:10.1038/s41467-023-43955-z

Large exchange bias enhancement and control of ferromagnetic energy landscape by solid-state hydrogen gating

Nat Commun. 2023 Dec 21;14(1):8510. doi: 10.1038/s41467-023-43955-z.

Authors

M Usama Hasan^{1

2}, Alexander E Kossak¹, Geoffrey S D Beach³

Affiliations

¹ Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
² Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology, Dhaka, 1000, Bangladesh.
³ Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA. gbeach@mit.edu.

Abstract

Voltage control of exchange bias is desirable for spintronic device applications, however dynamic modulation of the unidirectional coupling energy in ferromagnet/antiferromagnet bilayers has not yet been achieved. Here we show that by solid-state hydrogen gating, perpendicular exchange bias can be enhanced by > 100% in a reversible and analog manner, in a simple Co/Co_0.8Ni_0.2O heterostructure at room temperature. We show that this phenomenon is an isothermal analog to conventional field-cooling and that sizable changes in average coupling energy can result from small changes in AFM grain rotatability. Using this method, we show that a bi-directionally stable ferromagnet can be made unidirectionally stable, with gate voltage alone. This work provides a means to dynamically reprogram exchange bias, with broad applicability in spintronics and neuromorphic computing, while simultaneously illuminating fundamental aspects of exchange bias in polycrystalline films.

Abstract

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