(001)-oriented Ni80 Fe20 Mn100-x Ptx and Co90 Fe10 Mn100-x Ptx epitaxial bilayers were prepared using the molecular beam epitaxy method. Their exchange anisotropies were measured using a torque magnetometer, while their interfacial Mn uncompensated moments were measured by means of x-ray magnetic circular dichroism. The bilayers exhibited both one- and fourfold components in their anisotropy torque curves, which are difficult to explain using a simple model assuming the coherent rotation of ferromagnetic (F) and antiferromagnetic (AF) spins. Uncompensated Mn moments were confirmed to exist in the Mn100-x Ptx layer due to exchange coupling with the adjacent F layer, and the Mn moment of CoFe Mn100-x Ptx was found to be larger than that of NiFe Mn100-x Ptx. In order to understand the experimental results, we extended the Mauri [J. Appl. Phys. 62, 3047 (1987)] domain wall model by assuming cubic anisotropy in the AF and four AF domains whose interfacial moments are oriented along the principal axis of (001)-oriented Mn-Pt. The model predicted the uncompensated AF moment resulting from the domain wall formed in the AF layer and well reproduced the coexistence of one- and fourfold anisotropies in the in-plane torque curves. The uncompensated moment and torque curve were found to be dependent on the ratio of F/AF interfacial exchange coupling and the AF domain wall energy. By changing the ratio, it was possible to reproduce exchange anisotropy for various systems, such as NiFeMnPt, NiFeMnIr, and CoFeMnPt.
ASJC Scopus subject areas
- Physics and Astronomy(all)