Microstructure and magnetic properties of SmCo7/Co nanocomposite powders prepared by mechanical alloying

Abstract

SmCo7/Co nanocomposite powders were prepared by high-energy ball milling of SmCo5 modified by adding Co and annealed at different temperatures. The phase evolution, microstructure and magnetic properties of the nanocomposite powders were analyzed. The results have shown that the annealing temperature and the addition of Co significantly affected the phase structures and magnetic properties of the powders. The nanocomposite powders were completely composed of the SmCo7 phase and the face-centered cubic Co phase. When annealing the SmCo5 powder at 750 °C, the SmCo7 phase decomposed into Th2Zn17-type Sm2Co17 and CaCu5-type SmCo5 phases with an average grain size of 13.9 nm, and the maximum energy product and remanence had maximum values of 10.51 MGOe and 77.92 emu/g, respectively. However, adding 28 wt% Co effectively prevented growth of the grain (11.5 nm) and enhanced the decomposition temperature (850 °C), resulting in a higher maximum magnetic energy product, coercivity, and remanence. The SmCo7 lattice contracted as Co content increased.