Suppressing laves phase and overcoming magnetic properties tradeoff in nanostructured (Ce,La,Y)–Fe–B alloys via Ge substitution

Abstract

Developing permanent magnets based on full high abundance rare-earth (RE) elements of Ce, La, and Y offers tremendous potential for the balanced utilization of RE resources, but the magnetic properties of these magnets are restricted due to the magnetic dilution caused by the existence of the paramagnetic REFe2 laves phase. Herein, the non-RE element Ge with high efficiency was introduced to enhance the magnetic performance of Ce-, La-, and Y-based RE–Fe–B nanocrystalline alloys, and the highest maximum energy product [(BH)max] of 65.6 kJ/m3 and an enhanced coercivity (Hcj) of 346 kA/m were achieved in the [(Ce0.8La0.2)0.5Y0.5]16Fe77.5B6Ge0.5 alloy. This improvement is attributed to the increased content of the hard magnetic RE2Fe14B phase with refined grain size, which is further confirmed by micromagnetic simulation. First-principles calculations and a microstructure analysis reveal that the laves phase is effectively suppressed by Ge addition due to the formation of the Ce5Ge3 phase with the lowest formation energy. This work clarifies the positive role of Ge in simultaneously enhancing the Hci and (BH)max of nanostructured (Ce,La,Y)–Fe–B alloys.