The anisotropy of R2Fe17Cx (R=Sm and Tm)

The temperature dependence of the anisotropy field of Sm2Fe17Cx and Tm2Fe17Cx has been determined over the entire uniaxial ferro- or ferrimagnetic temperature range using the singularity point detection technique. The temperature dependence of the ac initial susceptibility was measured on these two systems from 4.2 to 300 K. The Curie temperature, lattice constants, spin-reorientation temperature (of Tm2Fe17Cx) and the magnetic anisotropy field are increasing with increasing carbon concentration. A ''magnetic-phase-like transition'' is observed in Sm2Fe17Cx for x<0.7 at low temperatures, which is proved not to be a spin reorientation. Additionally, the transition temperature increases systematically with increasing carbon concentration. However, the nature of this transition is not yet well understood