Mössbauer studies of α″-Fe16N2 and α′-Fe8N films

Conversion-electron Mossbauer spectra of epitaxial α″-Fe16N2 and α′-Fe8N films have been studied and their differences are discussed in detail. The Mossbauer spectrum of α″-Fe16N2 can be decomposed into three subspectra, which correspond to the 4d, 8h and 4c sites. The Mossbauer spectrum of α′-Fe8N can be fitted using four spectra based on a nitrogen-atom-random-distribution model. The average hyperfine field is larger (3%) for α″-Fe16N2 than for α′-Fe8N, which is approximately consistent with a 4.1% enhancement of the magnetic moments for α″-Fe16N2. The iron moments tend to locate in the film plane for α″-Fe16N2 and to arrange perpendicularly to the film plane for α′-Fe8N.