Review of Research and Development of Sm2Fe17Nx Hard Magnetic Material

Research and development of Sm2Fe17Nx hard magnetic materials is reviewed. In order to investigate the effects of different interstitial elements on the Th2Zn17 parent crystal structure and on the magnetic properties of the material, research on Sm2Fe17Cy compounds is also reviewed. The lattice constants a and c of Sm2Fe17Cy compounds (y≪1.5) gradually increase with increasing carbon content. Both Sm2Fe17Nx and Sm2Fe17Cy (x,y≫2.0) compounds exhibited nearly constant lattice expansion rates of 2.3% along the a-axis and 1.7% along the c-axis. No report has appeared on compounds for which 1.5≪(x or y)≪2. In Sm2Fe17Cy (y≪1.5) compounds, the unit cell volume and Curie temperature (Tc) increase with increasing carbon content. In Sm2Fe17Nx (2.1≪x≪3) compounds, however, a nearly constant unit cell volume and Tc are reported. The differences in the magnetic properties of Sm2Fe17Nx specimens prepared from the different starting alloys produced in various processes are reviewed. The mechanism of nitrogenation under various gas atmospheric conditions is also discussed and reviewed.