Micromagnetic Simulation Of Demagnetization Curves For Nanocrystalline NdFeB Magnets

Nanocrystalline NdFeB with excellent permanent magnet property have attracted much attention since the advent. People have study it's quality experimentally and theoretically. In 1996, Fischer,Schrefl et al firstly performed the calculation on the demagnetization curve of Nanocrystalline Nd₂Fe₁₄B by using the micromagnetic finite-element method and three-dimensional model. However, the quality of the calculation is not goodsuch as the calculated μ_0iH_c for the stoichiometric composition magnets ofdifferent grain sizes are larger than the experimental values of the Nd_2.33Fe₁₄B_1.06Si_0.2 magnets by 60%¹70% .This is unreasonable. Because the intergranular exchange interaction for the magnet of stoichiometric composition with Nd₂Fe₁₄B grains in direct contact is larger than that of Nd-rich magnets with a Nd-rich paramagnetic boundary phase separating the grains.The character of the Nanocrystalline NdFeB is determined by grain size and boundary phase. For the stoichiometric alloy, the adjacent Nd₂Fe₁₄B grains of the NdFeB magnet contact each other. But for the Nd rich magnet, the grains is surrounded by Nd-rich paramagnetic boundary layer. Many calculations has been performed on the demagnetization curve for stoichiometric Nanocrystalline Nd-Fe-B magnet with Nd₂Fe₁₄B grains at room temperature. While the study of the Nd-rich Nanocrystalline Nd-Fe-B is...