Improved magnetic properties by treatment of iron-based rare earth intermetallic compounds in anmonia

The R2Fe17 and R2Fe17C intermetallic compounds are found to absorb approximately two atoms of nitrogen per formula unit on heating in ammonia or nitrogen. The interstitial nitrides retain the original Th2Ni17 or Th2Zn17 structures, but with a large increase in unit cell volume (≈ = 7%). Curie temperatures of 420 °C are found when R = Y and 470 °C when R = Sm. There are also substantial increases in magnetisation and anisotropy field (when R = Sm). These new interstitia nitrides have excellent intrinsic magnetic properties for permanent magnet applications.