Chemical shift of the nitrogen electrons in Fe/sub 16/N/sub 2/[001] single crystal films epitaxially

The spectra of X-ray photoelectron spectroscopy (XPS) were measured for Fe₁₆N₂(001) single crystal films epitaxially grown by molecular beam epitaxy (MBE). It was found that the binding energy of N-1s (E _{N 1S}) of Fe₁₆N₂ is lower than that of Fe₄N, indicating that the energy level of N-1s electron in Fe₁₆N₂ is higher due to the larger value of the electron-electron Coulomb energy within N atom. From this result, it is expected that more electrons transfer from N atoms to N atoms in Fe₁₆N₂ than in Fe₄N. It is likely that the N atoms in Fe16N2 act as electron acceptors and this can lead to the nearly full spin polarization in each Fe atoms with a ferromagnetic coupling due to electron hopping.