Modeling of Nd-Oxide Grain Boundary Phases in Nd-Fe-B Sintered Magnets

摘要

We use atomistic and micromagnetic simulations combined with atomic-scale, aberration-corrected transmission electron microscopy to study the anisotropy profile of the interface between a Nd_2O_3-hP5 and a Nd_2Fe_(14)B phase. It is shown that a hybrid Morse-Buckingham potential approach can be used to study mixed-metallic and oxide-rich systems and to calculate surface-energy-induced large strains and potentially large relaxation effects on the adjacent grains. These are used to derive a magnetoelastic anisotropy energy from a first-order perturbation of the magnetoelastic Hamiltonian and are used to evaluate its effect on coercivity. It is shown that the change in coercivity originates from these distortions in the Nd_2Fe_(14) B crystal lattice close to the grain boundary, and the coercivity can be evaluated using such a multiscale modeling approach.