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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.
Date of Publication: Sept. 2003