Structure and Magnetic Properties of Mechanically Grinded γ'-Fe₄N Iron Nitride

Abstract

We have studied the structure and magnetic properties of mechanically grinded γ-Fe₄N iron nitride powder. During mechanical grinding (MG), γ-Fe₄N iron nitride initially changes to a bcc structure where the phase transformation is not completed. After 100h of MG, an amorphous-like phase is partially formed. Saturation magnetization (σ) and coercive force (Hc) improve due to the structure change of γ-Fe₄N and worsen with further MG. In the milled alloy of 300 h, α-Fe, γ-Fe₄N and α"-Fe₁₆N₂ phases appear after annealing at 673K, leading to the increase of saturation magnetization. However, after annealing above 873K, only α-Fe is retained owing to the vaporization of nitrogen atoms from Fe matrix.