Effect of grain boundary phase on the magnetization reversal process of nanocrystalline magnet using large-scale micromagnetic simulation

Abstract

We investigated the effects of grain boundary phases on magnetization reversal in permanent magnets by performing large-scale micromagnetic simulations based on Landau–Lifshitz–Gilbert equation under a periodic boundary. We considered planar grain boundary phases parallel and perpendicular to an easy axis of the permanent magnet and assumed the saturation magnetization and exchange stiffness constant of the grain boundary phase to be 10% and 1%, respectively, for Nd2Fe14B grains. The grain boundary phase parallel to the easy axis effectively inhibits propagation of magnetization reversal. In contrast, the domain wall moves across the grain boundary perpendicular to the easy axis. These properties of the domain wall motion are explained by dipole interaction, which stabilizes the antiparallel magnetic configuration in the direction perpendicular to the magnetization orientation. On the other hand, the magnetization is aligned in the same direction by the dipole interaction parallel to the magnetization orientation. This anisotropy of the effect of the grain boundary phase shows that improvement of the grain boundary phase perpendicular to the easy axis effectively enhances the coercivity of permanent magnets.

Relationship between magnetic nucleation and the microstructure of a hot-deformed permanent magnet: micromagnetic simulation

“…where A(x) is the exchange stiffness constant, M s is the saturation magnetization, K 1u is the uniaxial anisotropy constant, andê a is the easy axis [42][43][44][45] . The simulation model is segmented into 268,435,456 cubic cells of dimensions 2.0 × 2.0 × 2.0 nm 3 to simulate the magnetization dynamics using the finite-difference method under periodic boundary conditions.…”

Anisotropy of exchange stiffness based on atomic-scale magnetic properties in the rare-earth permanent magnetNd2Fe14B

“…Effective magnetic field on ith cell, H eff i , is defined as the derivative of the micromagnetic energy, E cont i (obtained from Eq. ( 2)), with respect to M i [47]:…”

Tuning the magnetic properties of hard–soft Ba0.5Sr0.5Fe10Al2O19 and Ni0.1Co0.9Fe2O4 nanocomposites via one pot sol–gel auto combustion method for permanent magnet applications

“…In the current scenario, it has consistently reduced with an increase in the content of the soft phase as shown in figure 10(e). As a result of the high dipole field and the lack of a potential barrier, the domain wall moves perpendicular to the easy axis, causing the nucleation field to diminish [73]. The Bohr magnetron (μ B ) was calculated and plotted in figure 10(f).…”