Exchange anisotropy of (0Â 0Â 1)-oriented Mn80Ir20/NiFe epitaxial bilayers

Exchange anisotropy was investigated for Mn80Ir20/NiFe epitaxial bilayers with (0 0 1)-orientation grown applying a magnetic field along either the [1 0 0] or the [1 1 0] direction and was compared with that for Mn89Pt11/NiFe bilayers. The Mn80Ir20/NiFe bilayers exhibited a large exchange bias field without post-annealing. Its easy direction of the unidirectional anisotropy was always parallel to the 〈110〉 direction. This result was similar to that of Mn89Pt11/NiFe bilayers. On the other hand, MnIr/NiFe bilayers showed magnetic anisotropy torque curves significantly different from Mn89Pt11/NiFe bilayers. Mn89Pt11/NiFe showed a very large 4-fold component while Mn80Ir20/NiFe showed a much smaller one.