X-ray magnetic circular dichroism studies of „001...-oriented NiFe/Mn100−xPtx exchange bilayers

001 -oriented Ni80Fe20/Mn100−xPtx and Co90Fe10/Mn100−xPtx 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 oneand 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−xPtx layer due to exchange coupling with the adjacent F layer, and the Mn moment of CoFe/Mn100−xPtx was found to be larger than that of NiFe/Mn100−xPtx. In order to understand the experimental results, we extended the Mauri et al. 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 oneand 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 NiFe/MnPt, NiFe/MnIr, and CoFe/MnPt. © 2006 American Institute of Physics. DOI: 10.1063/1.2388136