ON THE ITINERANT MAGNETISM OF MN AND ITS ORDERED ALLOYS WITH FE AND NI

Within a semi-empirical tight-binding method taking into account 3d-, 4s- and 4p-electrons we treat the itinerant magnetism of Mn and its ordered gamma-Ni3Mn and gamma-FeMn alloys. The spin polarization is generated self-consistently by the Hubbard mechanism. For a-Mn with its complicated spatial structure and essentially unknown, non-collinear spin configuration, we have calculated collinear and non-collinear spin structures, which we discuss in the light of the various experimental suggestions. For the simpler cases of gamma-Mn and the first-mentioned alloy, we find collinear spin structures in good agreement with experiments, whereas for the second alloy, which is disordered with a non-collinear spin configuration, only a collinear spin structure has been calculated. From the results we determine optimal choices for Hubbard's U-parameters as well as the relative band shifts for Mn, Fe and Ni, and show that the introduction of additional exchange interactions is not necessary within the accuracy of the approach.