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

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. (C) 2003 American Institute of Physics.