Influence of nitrogenation on structure development and magnetic properties of mechanically alloyed and annealed Sm- Fe powders

摘要

Sm-Fe-N compounds were prepared by mechanicalalloying, subsequent annealing and nitrogenation. For crystal structureinvestigations of the non-equilibrium phases Sm_2Fe_(17+y)Nxformed at various annealing temperatures T_A for 1 hX-ray diffraction with following Rietveld analysis was used. Avolume expansion of 6.2% was observed after nitrogenation. Asfor the non-nitrided Sm-Fe alloys a modified TbCu_7-typestructure (space group P6Immm) and a modified Th_2Zn_17-typestructure (space group R3m) have been observed. However, fornitrogenated Sm-Fe samples the modified Th_2Zn_17-typestructure forms already for annealing at T_A=750 deg C prior tonitrogenation. For samples annealed, prior to nitrogenation,between T =600 and 700 deg C the modified TbCu_7-typestructure was found, in which the nitrogen occupies randomly the3f position with an occupancy larger than 1/3. The partiallyordered, modified Th_2Zn_(17)-type structure by introducingadditional Fe(6c) and Sm(3a) structure formed for 75- deg C