Studies on the Structure and the Giant Magnetization of α"-Fe₁₆N₂

Abstract

  Mössbauer studies were carried out to clarify the magnetic structure and the formation process of α"-Fe₁₆N₂. To obtain α"-Fe₁₆N₂ samples, thin iron films were nitrified by a multiple implantation of nitrogen ions, followed by vacuum annealing at 150°C for 2 or 60 hours. Their Mössbauer spectra were decomposed into three sextets originated from three sites of Fe in α"-Fe₁₆N₂, and one of residual α-Fe. It was found that the nitrogen ions tend to order, so as to form α"-Fe₁₆N₂. Because of the tendency, the iron nitride has a structural resemblance with α"-Fe₁₆N₂ since ions were implanted. The annealing was effective to an additional improvement of the nitrogen order and a relaxation of internal stresses. Magnetic moment of each Fe atom corresponding to the three sextets was obtained to be 1.3, 2.5 and 3.8 μ_B, respectively. In α"-Fe₁₆N₂, the first neighbor Fe atom of nitrogen yields the least moment, and the third one yields the maximum moment.