Improvement of coercivity in Nd-Fe-B nanocomposite magnets

We examined the effects of Nd-Al alloy addition on the microstructures and magnetic properties of Nd4Fe77.5B18.5 nanocomposite magnets. The Nd4Fe77.5B18.5 nanocomposite magnet without Nd-Al alloy addition showed a coercivity of 0.18 MA/m, whereas that with the addition of 40% Nd-Al alloy exhibited a high coercivity of 1.44 MA/m. Microstructural studies revealed that the improvement of the coercivity of the nanocomposite magnets was due to an increase in the amount of the hard magnetic Nd2Fe14B phase. It was found that the Nd-Al alloy reacted with the soft magnetic Fe3B phase in the nanocomposite magnets during annealing and formed the Nd2Fe14B phase.