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/m3 to 0.80 T, 865 kA/m, and 104 kJ/m3 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.