16:00 〜 18:00
▼ [17p-P10-53] Angular-dependent exchange bias with competing anisotropies in epitaxial Co3FeN/MnN bilayers
キーワード：exchange coupling, MOKE
Exchange coupling between ferromagnets (FMs) and antiferromagnets (AFMs) is one of the important phenomena in spintronic devices. Therefore, the main properties of exchange coupling are well understood for, in particular, polycrystalline bilayers [1]. In the case of full epitaxial FM/AFM bilayers, the situation is more complex because of unusual magnetization switching processes resulting from competing anisotropies between a fourfold magnetocrystalline anisotropy and a unidirectional exchange coupling [2]. Up to now, we have clarified the unusual magnetization switching processes and angular-dependent exchange bias (Hex) effects in fully epitaxial Co3FeN/MnN bilayers, where the unidirectional exchange coupling has been applied along the easy axis of magnetocrystalline anisotropy of Co3FeN [3]. In this presentation, we present further studies of the relationship between magnetocrystalline anisotropy and unidirectional exchange coupling in fully epitaxial Co3FeN/MnN bilayers [4].
Figure 1 presents the angular-dependent Hex of Co3FeN/MnN bilayers obtained by longitudinal magneto-optic Kerr effect magnetometry, where the unidirectional exchange coupling is applied along easy (a) and hard axes (b) of Co3FeN fourfold magnetocrystalline anisotropy. The angular-dependent Hex exhibits 180° period for the sign switching of the exchange-bias field when the exchange coupling is parallel to the easy axis [Fig. 1(a)], while the angular-dependent Hex exhibits an approximately 45° period when the exchange coupling is parallel to the hard axis [Fig. 1(b)]. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent Hex reproduces the experimental results. At the presentation, we will show the change of angular-dependent Hex as a function of the ratio between exchange-coupling constant and magnetocrystalline anisotropy constant.
[1] J. Nogues et al., JMMM 192, 203 (1999).
[2] W. Zhang et al., APL 98, 092503 (2011).
[3] T. Hajiri et al., PRB 94, 184412 (2016).
[4] T. Hajiri et al., JPCM 30, 015806 (2018).
Figure 1 presents the angular-dependent Hex of Co3FeN/MnN bilayers obtained by longitudinal magneto-optic Kerr effect magnetometry, where the unidirectional exchange coupling is applied along easy (a) and hard axes (b) of Co3FeN fourfold magnetocrystalline anisotropy. The angular-dependent Hex exhibits 180° period for the sign switching of the exchange-bias field when the exchange coupling is parallel to the easy axis [Fig. 1(a)], while the angular-dependent Hex exhibits an approximately 45° period when the exchange coupling is parallel to the hard axis [Fig. 1(b)]. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent Hex reproduces the experimental results. At the presentation, we will show the change of angular-dependent Hex as a function of the ratio between exchange-coupling constant and magnetocrystalline anisotropy constant.
[1] J. Nogues et al., JMMM 192, 203 (1999).
[2] W. Zhang et al., APL 98, 092503 (2011).
[3] T. Hajiri et al., PRB 94, 184412 (2016).
[4] T. Hajiri et al., JPCM 30, 015806 (2018).