The effect of Co on the enhanced magnetic properties of Fe3B/Nd2Fe14B magnets

Abstract The addition of Co into Nd4Fe77.5−xCox(HfGa)yB18.5 (0⩽x⩽5, y=0, 0.5) was found to enhance the magnetic properties of Fe3B/Nd2Fe14B nanocomposite magnets. The enhancement resulted from the fact that Co retarded the crystallization of α-Fe or Fe3B but accelerated that of Nd2Fe14B. The decreased interval between the onset of crystallization temperature of Fe3B and Nd2Fe14B phases enabled the grain growth of each phase to be uniform during a post-annealing of the melt-spun ribbons. The addition of 3–5 at% Co into ternary composition Nd4Fe77.5B18.5 increased the coercivity ( i H c ) from 3.27 to 3.54 kOe with the enhanced remanence value (4πMr) around 11.54 kG. From the ribbon magnets of Nd4Fe71.5Co5Hf0.5Ga0.5B18.5 made at 26 m/s and annealed at 680°C for 10 min, the magnetic properties of Br=11.54 kG, i H c =3.54 kOe, and (BH)max=14.35 MGOe were obtained from volume production line.