  The mystery of giant saturation magnetization of Fe16N2 has remained for 37
years. In this letter, X-ray absorption spectroscopy (XAS) and magnetic
circular dichroism (XMCD) are used to study the electron states of Fe atoms in
Fe16N2 and Fe8N films. Localized Fe 3d electron states, which are not expected
from current theories (models), are observed. The XMCD spectra and elemental
hysteresis loops reveal the polarization of N atoms and the hybridization of N
and Fe atoms. This discovery points to the origin of giant saturation
magnetization in Fe16N2.
