Demagnetization curves at different temperatures for single-phase nanocrystalline Nd-Fe-B magnets studied micromagnetically

The demagnetization curves at different temperatures between 4 and 250 K we re calculated for single-phase nanocrystalline Nd-Fe-B magnets by using the micromagnetic finite-element technique. The calculations were carried out for a model magnet comprised of 216 grains of dimension 20 nm, taking into account the anisotropic characteristics of the curve with respect to the fi eld direction. The calculations simulate the experimental curves for the na nocrystalline Nd13Fe77B10 magnet fairly well. The inter-grain exchange inte raction in the magnet is estimated to be about 75% of the intra-grain excha nge interaction.