Exchange bias in ferromagnet/antiferromagnet bilayers

TLDR

Since the exchange bias (EB) effect was first discovered in Co/CoO core‑shell nanoparticles, it has been extensively studied in various ferromagnet/antiferromagnet bilayers because of its crucial role in spintronics devices. The article reviews the investigation of EB carried out by the authors’ research group. The review surveys EB fundamentals—including layer‑thickness, microstructure, and ferromagnet magnetization effects—examines positive and perpendicular EB mechanisms, demonstrates hysteretic angular dependence and training effects, and discusses the roles of rotatable anisotropy. They demonstrate hysteretic angular dependence of EB and analyze its training effect.

Abstract

Since the exchange bias (EB) effect was discovered in the Co/CoO core-shell nanoparticles, it has been extensively studied in various ferromagnet (FM)/antiferromagnet (AFM) bilayers due to its crucial role in spintronics devices. In this article, we review the investigation of the EB in our research group. First, we outline basic features of the EB, including the effects of the constituent layer thickness, the microstructure and magnetization of the FM layers, and we also discuss asymmetric magnetization reversal process in wedged-FM/AFM bilayers. Secondly, we discuss the mechanisms of the positive EB and the perpendicular EB. Thirdly, we demonstrate the hysteretic behavior of the angular dependence of the EB and analyze the EB training effect. Finally, we discuss the roles of the rotatable anisotropy in the two phenomena.