Micromagnetism simulation on effects of soft phase size on Nd2Fe14B/α Fe nanocomposite magnet with soft phase imbedded in hard phase

摘要

In this study, micromagnetism simulation by using finite difference method is carried out on the Nd2Fe14B/α-Fe nanocomposite magnet with soft phase imbedded in hard phase. The effects of soft magnetic phase size (S) on the magnetic properties and magnetic reversal modes are systematically analyzed. As S increases from 1 nm to 48 nm, the remanence (Jr) increases, while the coercivity (Hci) decreases, leading to the result that the magnetic energy prod-uct [(BH)max] first increases slowly, and then decreases rapidly, peaking at S=24 nm with the (BH)max of 72.9 MGOe (1 MGOe=7.95775 kJ·m?3). Besides, with the increase of S, the coercivity mechanism of the nanocomposite magnet changes from nucleation to pinning. Furthermore, by observing the magnetic moment evolution in demagnetization pro-cess, the magnetic reversal of the soft phase in the nanocomposite magnet can be divided into three modes with the increase of S:coherent rotation (S<3 nm), quasi-coherent rotation (3 nm≤S<36 nm), and the vortex-like rotation (S≥36 nm).