Structure and magnetic properties of bulk nanocrystalline SmCo6.6Nb0.4 permanent magnets

The crystal structure and magnetic properties were studied for the bulk nanostructural permanent magnet SmCo6.6Nb0.4 prepared by spark plasma sintering method. The magnet crystallizes in a single phase with a hexagonal TbCu7-type crystal structure after the sintering process. Rietveld fitting results show that the alloying element of Nb prefers to occupy the 3g site. Microstructure observation indicates that the average crystal grain size is about 30 nm. The coercivity decreases almost linearly from 2.8 to 0.5 T with increasing temperature from 300 to 773 K. A remanence enhancement resulting from intergrain exchange coupling among the fine grains was also observed. (c) 2007 American Institute of Physics.