Coercivity enhancement by adjusting the ratio of La to Ce in REFeB films

Abstract High abundant La and Ce elements have been supposed be a potential developing direction as the partial alternative to crucially relied Nd/Pr in the 2:14:1-type permanent magnets. In this work, we reported that adjusting the substitution ratio of La to Ce for inducing Ce valence is an effective strategy to prepare perpendicular magnetic anisotropic (LaxCe1-x)9Nd9Fe72B10 films (0 ≤ x ≤ 1) with good magnetic properties. Both X-ray diffraction and transmission electron microscopy results illustrate the lattice expansion of RE2Fe14B tetragonal phase after lanthanum partially replaces cerium element. The increase of La content in the composition range of x ≤ 0.7 benefits Ce valence shifting towards the favorable Ce3+ state as verified by X-ray photoelectron spectroscopy results, leading to the enhancement of coercivity. Combining with characterization of domain morphology and micromagnetic theory analysis, the coercivity mechanism of domain reversal has been confirmed that with the increasing La content, it gradually tends to a dominant domain-wall-pinning mechanism from a mixed mechanism of domain-wall-pinning and nucleation behaving together. Our results provide a feasible method to enhance magnetic properties of high abundant rare-earth permanent magnetic films by manipulating doping element contents and are helpful to understand magnetization reversal behaviors in the films.