Effect of exchange–coupling interaction on the effective anisotropy in nanocrystalline Nd2Fe14B material

Abstract The influence of exchange–coupling interaction on the effective anisotropy in nanocrystalline Nd2Fe14B permanent material has been investigated. The results show that the exchange–coupling interaction between grains causes a decrease of the effective anisotropy constant, Keff, with decreasing grain size. The variation of Keff with grain size is basically the same as that of coercivity. The decrease of the effective anisotropy is the main reason for the reduction of the coercivity. In order to get high anisotropy or coercivity in nanocrystalline Nd2Fe14B material, the grain size should be larger than 20 nm.