Impact of RE-rich phases on magnetic properties in RE–Fe–B-sintered magnets by Tb diffusion

We investigated the effect of Tb grain boundary diffusion on the structural transformation and magnetic properties across operational temperature ranges. Through micro-structural characterization, Fm3¯m-type and Ia3¯-type RE-rich phases were observed, and their effects on the magnetic properties were investigated. The distinct atomic distribution in the Ia3¯-type phase characteristic [111] zone axis was observed via HAADF images in the diffused magnet. The Ia3¯-type phase exhibited a lower lattice misfit with RE₂Fe₁₄B, favoring the formation of a larger nucleation field. The other grain boundaries with low coherence exhibit significant Cu enrichment. The lower lattice misfit and Cu-rich zone are critical for higher coercivity.