CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF A NITROGENATED MELT-SPUN SM2FE17 COMPOUND

Sm2Fe17N2.9 compound powders were prepared from parent alloys of Sm2Fe17 which were made by both arc melting and rapid solidification processes. The cast Sm2Fe17 contained mixed phases of SmFe3 and alpha-Fe, and correspondingly formed less Sm2Fe17Nx with a rather large amount of residual alpha-Fe after nitrogenation. The melt-spun Sm2Fe17 compound, however, was single phase and exhibited a negligible amount of residual alpha + Fe after nitrogenation. The residual amount of free iron was found to increase as a function of milling time and to impede the development of promising permanent magnetic properties. The melt-spun Sm2Fe17Nx compound powders exhibited a coercivity value (i)H(c) of 5 kOe, which is double that of the as-cast Sm2Fe17Nx powders and a high remanence B(r) = 60 e.m.u. g-1. The average magnetic moment of Fe atoms in the crystal is estimated to be 2.29 mu(B) and the Fe atom in the 6c site exhibits the highest magnetic moment of 2.65 mu(B). The expansion in the c axial direction of the nitrogenated crystal was found to be mainly due to extension of Sm(6c)-Fe(c) and Fe(18f)-Fe(18f) distances.