Composition-dependent magnetic properties of melt-spun La or/and Ce substituted nanocomposite NdFeB alloys

Aiming at high-performance low-cost NdFeB magnets, the magnetic properties and microstructure for melt spun nanocrystalline (Nd1−xMx)10Fe84B6 (M=La, Ce, or La0.5Ce0.5; x=0–0.7) alloys were investigated. Relatively, LaCe-substituted alloys show high values of the remanent magnetization Mr, the maximum energy product (BH)max and the coercivity Hc, up to 114 emu/g (1.07 T), 147 kJ/m3 and 471 kA/m, respectively, at x=0.1. The unusual increase in coercivity for the alloys with 10% La or 10% La0.5Ce0.5 substitution is possibly attributed to the phase segregation in alloys with certain La or LaCe contents. The reduced Curie temperature and spin-reorientation temperature were obtained for La, Ce or LaCe substituted alloys. Transmission electron microscope analysis has revealed that a fine and uniform distributed grain structure leads to remanence enhancement for La0.5Ce0.5 substituted alloys. The present results indicate that partially substituting Nd by La or/and Ce cannot only effectively reduce the cost of nanocrystalline NdFeB based magnetic powders but also can maintain a relatively good combination of magnetic properties.