Effects of Hot-Pressing Temperature on the Magnetic Properties of Hot-Pressed Nanocrystalline Nd–Fe–B Magnets

Bulk nanocrystalline Nd-Fe-B magnets are prepared by the hot-pressing method at different temperatures of 450 °C-650 °C. The initial magnetization curve changes from a single-phase magnetization for the magnets prepared below 600 °C to a two-phase magnetization for the magnets prepared at 650 °C. The Henkel plot is also measured to investigate the exchange coupling interaction, and the results show that two positive peaks occur on the δM curve for the magnet prepared at 650 °C. Scanning electron microscopy results show that the (Pr, Nd)-rich phase is aggregated along the gaps of the ribbons at 650 °C, and the (Pr, Nd)-rich phase behaves magnetically soft property. The inhomogeneous microstructure caused by the aggregation of (Pr, Nd)-rich phase with the temperature increase leads to the change in magnetization behaviors.