Ab-initio study of X-ray absorption and X-ray magnetic circular dichroism spectra of Mn2PtGa and Co2PtGa alloys

Using first-principles calculations based on density functional theory, we have studied the X-ray absorption spectra (XAS) and X-ray Magnetic Circular Dichroism (XMCD) spectra of Co2PtGa and Mn2PtGa alloys. Using relativistic calculations, we have estimated and analyzed the contribution of the orbital and spin moments to the total magnetic moment for the transition metal atoms, Pt, Co and Mn. It has been observed that while the ratio of orbital and spin magnetic moments of Pt atom in Co2PtGa in cubic phase is substantial, this is an order of magnitude lower in Mn2PtGa. On the other hand, this difference reduces drastically in case of the martensite phase. This signifies the crucial role of the neighborhood in determining the magnetic properties of these materials. Further, the XAS and XMCD spectra at the L2,3 edges of different constituent atoms in various materials have been analyzed. The results (peaks and shoulders present in these XAS and XMCD spectra) have been corroborated with the atom-projected unoccupied density of states of the respective materials.