Synthesis and magnetic properties of α″-Fe16N2 nanofibers prepared by an electrospinning method

Although the iron-nitride α″-Fe16N2 phase exhibits excellent magnetic properties, its poor thermal and phase stability pose challenges in the fabrication of bulk-type samples. In particular, the low nitriding temperature, below 200 °C, increases possibility of forming the stable nitride phase with higher nitrogen content on the surface due to the slow diffusion rate of nitrogen atoms. To overcome this problem, it is crucial that the α-Fe precursors are small in size, well-dispersed, and that the post-heat treatment is conducted below 200 °C. In this study, we successfully demonstrated the fabrication of α″-Fe16N2 nanofibers through electrospinning process and a two-step heat treatment procedure involving hydrogen reduction at 290 °C for 2 h, followed by nitration at 160 °C for 12 h in an ammonia gas flow rate of 1.5 L/min. Furthermore, these α″-Fe16N2 nanofibers exhibited a saturation magnetization (M2.5T) of 182 emu/g, a residual magnetization (Mr) of 76.1 emu/g, and a coercivity (Hc) of 1.29 kOe.