Structure and Magnetic Properties of Fe16N2 Films Prepared by Nitrogen Ion Implantation

Iron nitride films with large magnetization were prepared by nitrogen ion implantation into iron films. The saturation magnetization of the iron nitride films increased with increasing nitrogen concentration, and the highest value was obtained at the stoichiometric concentration of α"-Fe₁₆N₂ (11.1 at% N). X-ray analysis revealed that the iron nitride produced was composed of α'-martensite and α"-Fe₁₆N₂. It was concluded that the increase in saturation magnetization was due not only to α"-Fe16N2, but also to α'-martensite. The saturation magnetization of the iron nitrides was found to be 257 emu/g. Mössbauer spectra of the iron nitrides were fitted by three Fe sextets with hyperfine fields of 400, 325 and 290 kOe. The magnetic moment of Fe with the highest hyperfine field was estimated to be about 3.5 μ_B.