Effect of Cu doping and annealing treatment on the microstructure and magnetic properties of nanocrystalline single-phase Nd-Fe-B alloys

The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Nd12.3Fe81.7-xCuxB6 (x=0-1.2) ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550°C for 15 min, which only contained Nd2Fe14B phase. The remanence, coercive force, and maximum energy product increase by 18.4%, 36.2%, and 49% respectively compared with those of Cu-free samples. The significant improvement in magnetic properties originates from the finer grains of the samples by introducing Cu, which leads to the stronger exchange-coupling between neighboring grains.