Hybrid Effect of Exchange Coupling in Ce–Pr–Nd–Fe–B SPSed Magnets by Adding Pr–Fe–B Alloys

In order to obtain high magnetic properties in Ce-Pr-Nd-Fe-B spark plasma sintered (SPSed) magnets, the alloys were introduced by the dual-alloy method. The relationship of microstructure, magnetic properties, and thermal stability was investigated. The remanent magnetization, coercivity, and maximum energy product were sharply enhanced from 0.68 T, 653 kA/m, and 75.62 kJ/m
³
to 0.80 T, 865 kA/m, and 104 kJ/m
³
for the magnets that with 0 and 75 wt.% Pr-Fe-B addition. The Curie temperature also increased from 542 K to 563 K after adding Pr-Fe-B alloys. The scanning electron microscopy (SEM) analysis showed that, during the sintering process, the rare-earth elements migrated into the flake boundary and diffused in 2:14:1 main phases; thus, (Ce, Pr, Nd)2Fe14B hard magnetic phases were formed, which is helpful to optimize the microstructure and magnetic properties. An enhancement of exchange coupling among the grains of SPSed magnets was obtained as a result of grain refinement by adding Pr-Fe-B alloys.