Preparation and Magnetic Properties of the Exchange Coupling NdFeB Nanocomposited Permanent Magnets

The effect of indium additions on the microstructures and magnetic properties of Nd₉Fe_85−xB₆In_x (x = 0–2) nanocomposites prepared by melt spinning was investigated. It was found that a certain amount of indium added to Nd₉Fe₈₅B₆ magnets enhances the hard magnetic properties. The coercivity and remanence ratio of the magnet with 0.5 at.% indium increases from 405kA/m (no indium) to 465kA/m and from 0.7 to 0.86 respectively. Squareness of its hysteresis loop is also improved greatly. The optimum energy product (BH)max increases remarkably from 95kJ/m³ to 145kJ/m³. The origin for those enhancements is mainly attributed to the magnetically softened grain boundaries and enhanced crystallographical coherency by indium addition. The magnetic annealing is found to be helpful to enhance the coherency and coupling between hard and soft phases.