Usage of Ce for the intrinsic properties of rare-earth permanent magnets

Utilities of valence fluctuation effects in Ce are identified for magnetic anisotropy, magnetization, Curie temperature, and structure stability, all of which are of crucial importance in rare-earth permanent magnets. Enhancement of an intrinsic coercivity is demonstrated on the Co-rich side of Ce(Co,Cu)₅ experimentally and correspondingly we show theoretically that the crossover near a valence transition of Ce brings about an order of magnitude enhanced magnetic anisotropy. Magnetization can actually benefit from Ce⁴⁺ with the volume effect and a particular site preference in the multiple-sublattice ferromagnets being taken into account. There can be a trade-off among those preferred properties for rare-earth permanent magnets and we discuss a resolution of it based on an importance sampling approach in the virtual materials space.