The crystal structure and magnetic properties of R₂Fe₁₇C_x (x=1.5 and 2.0) prepared by the melt-spinning method

The authors have successfully prepared the carbides R₂Fe₁₇C_x (R identical to Y, Gd, Tb, Dy, Ho and Er) with a high carbon content x=1.5 and 2.0 by the melt-spinning method. The carbides have a single rhombohedral Th₂Zn₁₇ structure phase and are highly stable to at least 1100 degrees C. The Curie temperatures T_C are raised enormously and the saturation magnetizations change little upon carbonation. The average enhancements of T_C are about 220 K for R₂Fe₁₇C_1.5 and 265 K for R₂Fe₁₇C_2.0. The volume dependence of the exchange interaction has been discussed. The Curie temperatures are analysed in terms of a mean-field model. The spin reorientation is observed to be 133 K for Er₂Fe₁₇C_1.5 and 141 K for Er₂Fe₁₇C_2.0.