Direction and size of Ir magnetic moment induced in MnIr/Co _1-xFe_x exchange bias bilayers from resonant x-ray magnetic scattering experiments at the Ir L₃ absorption edge

Interface magnetism was investigated for Ir atoms in Mn₇₃Ir ₂₇/Co₇₀Fe₃₀ and Mn₇₇Ir ₂₃/Fe bilayers which showed an exchange bias effect. Scattering angle and X-ray energy dependent resonant X-ray magnetic scattering patterns were measured at a small angle region around the Ir L₃ absorption edge to determine the induced magnetic structure of the Ir 5d magnetic moment. It is found that the induced Ir magnetic moment which follows applied field reversal is concentrated at the first atomic layer of the antiferromagnetic MnIr layer for both MnIr/CoFe and MnIr/Fe samples. The direction of the Ir moment is parallel to the magnetic moment of the ferromagnetic layer independent of the composition of the ferromagnetic layer. This behavior is different from that reported on the uncompensated 3d magnetic moment of Mn atoms. The average size of the Ir moment in the MnIr/CoFe bilayer is estimated to be about 1.4 times larger than that in the MnIr/Fe bilayer. These results are consistent with a first-principles band calculation.