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

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
_d
is widened by an increase in the size of the non-magnetic phase and that the ratio of the spatial size of H
_d
to 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
_N
at high temperatures.