Strategy to improve magnetic property of sintered (Nd, Ce)–Fe–B magnets: Moderate replacement of cerium with lanthanum

In this work, we proposed a method to enhance the magnetic properties of (Nd, Ce)–Fe–B magnets with Ce/TRE ratios below 25 wt% by introducing a moderate amount of La elements. The segregation behavior of La elements towards grain boundaries (GBs) was utilized to optimize the GB phase structure. Incorporation of La atoms into the main phase induces lattice expansion, leading to an increased formation of Ce3+ ions with enhanced magnetic moments. Comparative analysis with the original magnet (La/Ce = 0 wt%) demonstrates that the magnet with a La/Ce ratio of 10 wt% exhibits improvements of 0.3% in remanence, 12.6% in coercivity, and 0.6% in maximum energy product. These results underscore that the moderate addition of La elements enhances the fluidity of the rare earth-rich phase and optimizes the distribution of lamellar GB, consequently reinforcing the magnetic isolation effect. Furthermore, the promotion of the transformation from Ce4+ to Ce3+ ions contributes to the comprehensive enhancement of the magnetic properties. This research offers a novel strategy for fabricating high-performance and resource-efficient sintered magnets based on LaCe alloys.