⁵⁷Fe Mössbauer study of FeN_x (x=0.25≈0.91) alloys

Abstract

⁵⁷Fe Mössbauer measurements have been perforned at the first time on iron nitrides, FeN_x(x>0.5), films prepared by rf sputtering and the measurements for γ-FeN_0.09, γ'-Fe₄N, ε-Fe_2–3N and ζ-Fe₂N have been also performed. Two new phases for x>0.5 have been identified: One has a ZnS-type structure denoted by γ" Another phase is denoted by γ''' in which iron atoms constitute a fcc lattice but the details of occupation sites of nitrogen atoms are not yet clear. The isomer shift of γ" relative to α-Fe at 300 K is rather small in comparison with that of other well known nitrides. The roam temperature Mössbauer spectra of γ''' consist of a sum of two doublets. Mössbauer spectra of γ" at 10 K do not indicate magnetically split pattern, but those of γ''' show magnetically split patterns at 10 K with the hyperfine fields of 30 T and 48 T, respectively. The component of 48 T is due to oxides, not due to nitrides.