Exchange-coupling interaction and effective anisotropy in nanocomposite permanent materials

Taking Nd₂Fe₁₄B/α-Fe as example, the exchange-coupling interactions between magnetically soft and hard grains in nanocomposite permanent materials and their effects on the effective anisotropy of materials were investigated. The calculation results expressed that the exchangecoupling interactions are enhanced with the reduction of grain size, and the effective anisotropy of materials decreases with the reduction of grain size and the increase of magnetically soft phase component. The remanence and the effective anisotropy of materials possess the opposite variation trend with the change of grain size and phase ratio. The mean grain size should be in the range of 10–15 nm and the ratio of soft phase should be less than 50% for getting the magnet with high energy product.