Nitridation process effect on crystal structure and magnetic properties of TbCu7-type SmFe9 alloys

The effect of nitridation process, i.e. temperature and time, on crystal structure and magnetic properties of SmFe9Nx interstitial compounds was systematically investigated. After nitridation treatment, nitrogen atoms were incorporated into SmFe9 alloys to form SmFe9Nx interstitial compounds, which increased the distance of Fe-Fe and enhanced Fe-Fe interaction. As a result, SmFe9Nx interstitial compounds had a higher Curie temperature and more excellent magnetic properties than SmFe9 alloys. The relationships between nitridation temperature, nitridation time, nitriding efficiency, magnetic properties and phase transition were researched. It could be concluded that nitriding efficiency was strongly associated with magnetic properties and phase transition at different temperatures. The nitriding efficiency also had a connection with magnetic properties under different time, while no obvious phase transition was found during that process. By studying nitridation process under a series of temperatures and time in this experiment, a suitable nitridation temperature (713 K) and an ideal length of nitridation time (8 h) was decided, which would produce the optimal magnetic behavior of SmFe9Nx interstitial compounds.