Mössbauer spectroscopy of disordered and ordered iron–nitrogen solid solutions

Mössbauer spectroscopy has been used to study the distribution of nitrogen atoms in FeN solid solutions with high nitrogen content. It demonstrates the ordering of nitrogen in the b.c.t. solution at low temperatures, since a 400 kOe hyperfine environment appears. A new hyperfine interpretation of the f.c.c. solution shows a more effective contribution to the iron 3d band from nitrogen than from carbon. Hyperfine field data exhibit a localized negative and positive contribution at first and second nearest Fe neighbours respectively in the disordered b.c.t. solutions. Comparison with the case of carbon and isomer shifts favour 4s spin density oscillations consistent with the ordered Fe16N2 hyperfine data. Quadrupole shifts lead to a [001] or [110] spin polarization.