Electronic structure and x-ray magnetic circular dichroism inCu3Au-type transition metal platinum alloys

The electronic structure and x-ray magnetic circular dichroism (XMCD) in $X{\mathrm{Pt}}_3(X=$ V, Cr, Mn, Fe, Co, Ni) and $X_3\mathrm{Pt}(X=$ Fe, Co, Ni) compounds are investigated theoretically from first principles, using the fully relativistic Dirac LMTO band structure method. The electronic structure is obtained with the local spin-density approximation (LSDA). Theoretically calculated spin and orbital magnetic moments are found to be in good agreement with neutron and XMCD experimental data. An interpretation for systematic trends seen in the orbital and spin magnetic moments of the series $X{\mathrm{Pt}}_3$ is presented by analyzing the calculated spin- and orbital-projected density of d states. The important role of hybridization between the $3d$ transition metal and Pt d states in the formation of the orbital magnetic moments at the Pt site is emphasized. The x-ray absorption spectra as well as the x-ray circular magnetic dichroism at the K, $L_{2,3},$ and $M_{2,3}$ edges for transition metal sites and $L_{2,3},$ $M_{2,3},$ $M_{4,5},$ $N_{2,3},$ $N_{4,5},$ $N_{6,7},$ and $O_{2,3}$ edges for Pt sites are calculated for all nine compounds. Good agreement between theory and the experiment is obtained. The XMCD sum rules are used to compute the spin and orbital magnetic moments and the results are compared to the direct calculations.