Electronic structure of Co-Pt alloys: X-ray spectroscopy and density-functional calculations

The K and L-2,L-3 absorption edges and core-level binding-energy shifts for pure Co and Pt, and Co-Pt alloys are measured to investigate the changes in electronic structures of Co-Pt alloys. The results agree well with those of the first-principles calculations of the electronic structures by using a full-potential linearized-augmented-plane-wave method. It is found that there is an enhancement of the hybridization between the Co 3d and Pt 5d orbitals upon alloying. Consequently, as the Pt concentration increases, both Pt and Co gains d electrons, and there is a concomitant decrease in s and p electrons at both sites. This enhanced hybridization in the alloy leads to a net charge transfer from the Co to Pt site in accordance with the predictions based on the electronegativity. For the core-level shifts in Co-Pt alloys the initial-state effects are more important to the Pt 4f level, while the relaxation effects play a more important role for the Co 2p level.