抄録
Disordered γ-phase antiferromagnetic Mn alloys bring about an exchange bias when the antiferromagnetic spin exhibits the triple Q spin structure. Since a certain amount of cubic anisotropy is possibly realized in the disordered γ-phase antiferromagnetic alloys, model calculations to determine the exchange bias in an antiferromagnetic (AFM)/ferromagnetic (FM) bilayer have been performed for the antiferromagnetic layer with a cubic anisotropy. The present calculations reveal that the formation of the interfacial domain wall in the antiferromagnetic layer predominates the exchange bias and that the critical cubic anisotropy DC is defined by the domain wall width. In the torque curves calculated, as a function of the cubic anisotropy energy, a symmetric magnetic anisotropy curve in the ferromagnetic layer is clearly observed when no exchange bias field can be obtained. When a strong exchange bias is observed, on the other hand, the sinusoidal shape of the torque curve of the ferromagnetic layer disappears, showing a close relationship with the appearance of the exchange bias. From the present theoretical results, it is verified that the cubic anisotropy in the disordered AFM γ-phase alloys is closely associated with the exchange bias characteristics as well as the shape of torque curves of the AFM/FM bilayer.
