Development of Nd-Fe-B anisotropic bonded magnet with 27 MGOe

The maximum energy product of bonded magnets is advancing every year. The highest maximum energy product of any bonded magnet achieved is 25 MGOe (200 kJ/m³) in the Nd-Fe-B system by d-HDDR treatment. There is a great demand for even higher energy bonded magnets with the desire for smaller, more efficient electric motors. Bonded magnets made from d-HDDR treated anisotropic magnet powder have low squareness due to low squareness of the powder. The authors developed a method to increase squareness of d-HDDR powder, and succeeded in developing the world´s highest energy bonded magnet with 26.6 MGOe (213 kJ/m³). This was achieved through Dy-diffusion treatment followed by d-HDDR treatment, as well as an increase in the density of the bonded magnet. This magnet has little aging loss after being held at 393 K for 878 h.