A MICROMAGNETIC UNDERSTANDING OF THE POSTANNEALING PROCESS IN PRODUCING SINTERED ND-FE-B PERMANENT-MAGNETS

A micromagnetic analysis of the temperature dependence of the coercivi ty of sintered Nd-Fe-B permanent magnets with and without post-anneali ng treatment has been made based on the nucleation mechanism. Two temp erature ranges in which different mechanisms control the coercivity ar e clearly distinguishable. From the micromagnetic point of view, the p ost-annealing process reduces the local effective demagnetizing field (-N(eff)M(s), which makes the nucleation of a reversed domain more dif ficult, and therefore enhances the coercivity.