Effect of precursor state on the formation of triphase (SmCo7 + SmCo3)/Fe(Co) magnets

Abstract

The combination of fabrication of a precursor and subsequent thermal treatments is an effective strategy for crafting multi-phase SmCo-based nanocomposite magnets. However, a comprehensive understanding of the effect of precursor state on the formation of multiphase magnets has yet to be fully explored. In this study, Sm(CoFeCuZr)/Fe(Co) of precursors were prepared via mechanical alloying. The precursor state was tailored by adjusting the ball milling process, as well as the content and composition of soft magnetic phase. The amorphization degree of the SmCo phase, the atomic ratio of Sm:Co in the SmCo alloy, and the content of Fe(Co) in the precursor increase with the increasing ball milling time, the increase in the content of the soft phase and the proportion of Fe within the soft phase. And this resulted in an increase in the content of Fe(Co) and SmCo3 phases but a decrease in the content of SmCo7 phase in samples annealed at 400–720 °C. This further led to an increase in the saturation magnetization and a decrease in the coercivity of the triphase (SmCo7 + SmCo3)/Fe(Co) magnet. The mechanisms responsible for the precursor state control and the formation of the triphase magnet were investigated.