Structure and magnetic properties of bulk nanocrystalline SmCo7−xHfx sintered magnets

The structure and magnetic properties of the bulk nanocrystalline SmCo7−xHfx (x=0,0.1,0.2) magnets prepared using the spark plasma sintering technology were studied. SmCo7−xHfx magnet exhibits a single phase with the TbCu7-type structure. The Rietveld structure refinement results show that Hf prefers to occupy the 1a site, which in turn leads to an enhancement of the anisotropy field of the SmCo7 compounds. Microstructure analysis indicates that the average grains size is about 35nm. With increasing Hf contents from x=0 to 0.2, the coercivity increases from 0.89to2.08T. The coercivity of SmCo6.8Hf0.2 magnet decreases almost linearly from 2.08to0.4T with increasing temperatures from 300to773K.