Ab initio ground state and L-2,L-3 x-ray magnetic circular dichroism of Mn-based Heusler alloys

Relativistic full-potential calculations within the generalized gradient ap proximation (GGA) for a series of Mn-based Heusler alloys are presented. Ca lculated equilibrium lattice parameters deviate less than 1.2% from the exp erimental values. The main features of a half metallic system are present i n the density of states for the PtMnSb and NiMnSb. We predict that PdMnSb s hows half metallic character under hydrostatic pressure. The substitution o f Sb in PtMnSb by Sn or Te destroys the minority spin band gap. Spin and or bital magnetic moments for all the systems are in good agreement with previ ous calculations and experimental data. L-2,L-3 x-ray absorption and x-ray magnetic circular dichroism (XMCD) spectra are calculated for all the five compounds. Pt spectra present big deviations from system to system in the P tMnY (Y=Sn,Sb,Te) compounds while Mn spectra show only small deviations. Fo r all these spectra GGA underestimates the L-3/L-2 integrated branching rat io and produces a much smaller L-2 peak intensity for the Ni site in NiMnSb . The XMCD sum rules are used to compute the spin and orbital magnetic mome nts and the results are compared to the direct calculations.