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 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−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)-...