High coercivity SmCo5 synthesized with assistance of colloidal SiO2

Abstract

SmCo 5 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 5 with optimal size and high coercivity. In this paper, we report on the successful synthesis of phase pure SmCo 5 with spherical/prolate spheroids shape. Size control is obtained by utilizing colloidal SiO 2 as a template preventing aggregation and growth of the precursor. The amount of SiO 2 nanoparticles (NPs) in the precursor tunes the average particle size (APS) of the synthesized SmCo 5 with particle dimension from 740 to 504\xa0nm. As-prepared pure SmCo 5 fine powder obtained from using 2\xa0ml SiO 2 suspension possesses an APS of 625\xa0nm and exhibits an excellent coercivity of 2986 kA m −1 (37.5 kOe) without alignment of the particles prior to magnetisation measurements. Comparing with a reference sample prepared without adding any SiO 2 NPs, an enhancement of 35% of the coercivity was achieved. The improvement is due to\xa0phase purity, stable single-domain (SSD) size, and shape anisotropy originating from the prolate spheroid particles.