High coercivity SmCo synthesized with assistance of colloidal SiO.

SmCo is one of the most promising candidates for achieving a hard magnet with a high coercivity. Usually, composition, morphology, and size determine the coercivity of a magnet, however, it is challenging to synthesize phase pure SmCo with optimal size and high coercivity. In this paper, we report on the successful synthesis of phase pure SmCo with spherical/prolate spheroids shape. Size control is obtained by utilizing colloidal SiO as a template preventing aggregation and growth of the precursor. The amount of SiO nanoparticles (NPs) in the precursor tunes the average particle size (APS) of the synthesized SmCo with particle dimension from 740 to 504 nm. As-prepared pure SmCo fine powder obtained from using 2 ml SiO suspension possesses an APS of 625 nm and exhibits an excellent coercivity of 2986 kA m (37.5 kOe) without alignment of the particles prior to magnetisation measurements. Comparing with a reference sample prepared without adding any SiO NPs, an enhancement of 35% of the coercivity was achieved. The improvement is due to phase purity, stable single-domain (SSD) size, and shape anisotropy originating from the prolate spheroid particles.