Design of novel quasi-trivalent dual-main-phase Ce magnets with high performance by manipulating the chemical state of Ce

The application of Nd-Fe-B magnet with substitution of Nd by cheap and abundant Ce elements is seriously limited due to the intrinsically inferior magnetic properties of Ce-Fe-B. This work demonstrated a design of novel quasi-trivalent dual-main-phase (Nd, Ce)-Fe-B magnets (DMP Ce magnets) using the strategy of two main phases with giant magnetic anisotropy energy gap (MAEG). The maximum energy product of DMP Ce magnet with 40% weight percentage of Ce over total rare earth is optimized to be 40.57 MGOe, which is the energy-product record of high Ce-content (Nd, Ce)-Fe-B magnet. The superior magnetic properties are closely corelated to the valence of Ce. The average valence of Ce in the DMP magnets was quasi-trivalent, proved by XPS, which was lower than that in the single-main-phase magnets (+3.23). Furthermore, the isostructural heterogenous configuration in the DMP magnets could manipulate the chemical state of Ce and induce magnetic Ce3+ in the main phase, thereby improving the remanence. It was possible to control the Ce valence for designing novel high-performance Ce magnets using different main phases with diversity of MAEG. This would undoubtedly provide ideas for researching and developing new rare earth materials with a synergistic composition and structure.