Structure and magnetic properties of R2Fe17Cx (x∼2.5)

A series of rare-earth iron carbides were prepared by heat treatment of R2Fe17 compounds in methane. The nominal composition of these carbides is R2Fe17Cx, x∼2.5. The carbides retain the original Th2Zn17 or Th2Ni17 structure with a 6.5% volume expansion over the carbon-free unit cell. For Sm2Fe17C2.5, the Curie temperature is 760 K and the easy magnetization direction is along the c axis. The anisotropy field of Sm2Fe17C2.5 at room temperature is 15±0.5 T.