Magnetic properties of a new series of rare-earth iron nitrides: R ₂ Fe ₁₇ N y (y approximately 2.6)

A series of interstitial ternary nitrides R 2 Fe 17 N y with 2.3<y<2.9 has been prepared for R=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu and Y. The nitrides have structures related to those of Th 2 Zn 17 or Th 2 Ni 17 , but the unit cell volumes are 6-7% greater, and the magnetic ordering temperatures some 400 K higher than for the 2:17 parent compounds. The Fe-Fe exchange interactions are more than doubled by nitrogenation, whereas the R-Fe exchange interactions are little changed. All compounds exhibit easy-plane anisotropy at room temperature, except for Sm 2 Fe 17 N y , which is easy-axis.