Micromagnetic simulation of the effect of grain boundaries and secondary phases on the magnetic properties and recoil loops of hot-deformed NdFeB magnets

Abstract

Abstract Hot-deformed NdFeB magnets have attracted considerable attention due to their high thermal stability and exceptional corrosion resistance. In this study, the dependence of magnetic properties and recoil loops on the presence of a grain boundary phase (GBP) and Nd-rich secondary phases in hot-deformed NdFeB magnets was explored using micromagnetic simulations. By adjusting the parameters of the simulation model, the influence of several factors (thickness and spontaneous magnetization (Ms) of the GBP, Ms, total volume fraction and spatial distribution of the secondary phase), on the main and recoil loops was investigated. A change in thickness and in Ms of the GBP affects the coercivity (Hc) and remanence of the main loop. In particular, an increase of Ms leads to a decrease in the magnet’s Hc. The influence of the secondary phase depends on its spatial distribution. Large volume grains result in lower Hc, but the role in decreasing Hc is weaker in contrast to a random distribution of smaller grains of the same overall volume content. Open recoil loops were interpreted by analyzing the distribution of calculated magnetic moments and energy terms. Loop opening is not directly related to Hc of the main loop. Rather it is mainly due to small irreversibilities in the dipolar energy of different magnetic configurations that appear along the recoil loop.