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 Fe
₁₆
N
₂
(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 Fe
₁₆
N
₂
is lower than that of Fe
₄
N, indicating that the energy level of N-1s electron in Fe
₁₆
N
₂
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 Fe
₁₆
N
₂
than in Fe
₄
N. 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.