Exchange anisotropy of (001) oriented Mn1−xPtx/NiFe epitaxial films

Abstract

Exchange anisotropy was investigated for Mn1−xPtx (x=0.06–0.40)/NiFe bilayers prepared by molecular-beam epitaxy on MgO (001) substrates. The bilayers exhibited a large exchange bias field without postannealing, which showed a maximum value of 140–160 Oe around x=0.11. This result is almost the same as those for the (111) oriented bilayers. The exchange anisotropy is induced with the easy direction parallel to the 〈110〉 axes in spite of the fact that the magnetic field is applied along the 〈100〉 direction during the deposition. Diffraction peaks from an ordered phase of Mn3Pt alloy were not observed in the reciprocal space map measured by x-ray diffraction. The origin of the exchange anisotropy is attributed to the antiferromagnetic spin arrangements of the MnPt layer with a disordered face-centered-cubic structure.