Abstract
Abstract
Exchange bias (EB) occurring in ferromagnetic (FM)/antiferromagnetic (AFM) bilayers conventionally can lead to a unidirectional magnetic anisotropy (
K
eb
) as well as an accompanied uniaxial magnetic anisotropy (
K
u
). We observed an additional fourfold magnetic anisotropy (
K
4
) induced by interfacial exchange coupling in amorphous CoFeB/epitaxial IrMn bilayers with an EB. Because of the combined effect of the three kinds of magnetic anisotropies, one- and two-step magnetic switching processes were observed at different magnetic field orientations, which usually appear in single-crystal FM layer with an intrinsic magnetocrystalline anisotropy but not in amorphous FM layer. The angular dependent magnetic switching fields can be nicely fitted by a phenomenological model based on domain wall nucleation and propagation with the in-plane
K
4
along <100>. The ferromagnetic resonance measurements indicate that the specific strength of
K
4
for EB along [100] is larger than that for EB along [110]. The induced
K
4
can be understood by considering two types of AFM domains caused by both monatomic steps and defects and their induced net uncompensated spins along the in-plane <100> axes. The different dependence of
K
4
on the EB direction are because of the different effects of growth magnetic field on the presence of AFM domains.
Funder
National Natural Science Foundation of China
Natural Science Foundation of Shanghai
Subject
General Physics and Astronomy
Cited by
3 articles.
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