Preferred site occupation of 3d atoms in NixFe4-xN (x=1 and 3) films revealed by x-ray absorption spectroscopy and magnetic circular dichroism

X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism measurements were performed at the Ni and Fe L-2,L-3 absorption edges for NixFe4-xN (x = 1 and 3) epitaxial films. Spectral line-shape analysis and element-specific magnetic moment evaluations are presented. Shoulders at approximately 2 eV above the Ni L-2,L-3 main peaks in the XAS spectrum of Ni3FeN were interpreted to originate from hybridization of orbitals between Ni 3d at face-centered (II) sites and N 2p at body-centered sites, while such features were missing in NiFe3N film. Similar shoulders were observed at Fe L-2,L-3 edges in both films. These results indicate that the orbitals of Ni atoms did not hybridize with those of N atoms in the NiFe3N film. Hence, Ni atoms preferentially occupied corner (I) sites, where the hybridization was weak because of the relatively long distance between Ni at I sites and N atoms. The relatively large magnetic moment deduced from sum-rule analysis of NiFe3N also showed a good agreement with the presence of Ni atoms at I sites.