Increase in Nucleation Field of Nanocrystalline Nd(Fe,Co)B Magnets Due to Strengthening of Exchange Interaction—Computer Simulation

摘要

The effect of the strength of exchange interaction on the nucleation field HN was studied by computer simulation with varying temperature as well as the size of the non-magnetic phase for Nd(Fe,Co)B magnets composed of fine grains. It was clarified that the spatial distribution of demagnetizing field H_dis widened by an increase in the size of the non-magnetic phase and that the ratio of the spatial size of H_dto the exchange length Lex is an important factor of determining H_N. Resultantly, the increase in the exchange strength increased H_N. Based on this calculation result, magnetic properties of Nd(Fe,Co)B magnets were simulated and it was found that a small amount of substitution of Co for Fe increases Lex and resultantly improves H_Nat high temperatures.