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A New Method for Enhancing the Coercivity of NdFeB Permanent Magnets without Dy

2010.08.31

This research was headed by
Kazuhiro Hono

An exquisite natural phenomenon that polarity-induced assembly of crystals can occur was discovered. A ZnO rod has a positive and a negative polar end and in a concentric assembly, all rods grow along a single polar end, resulting in different properties. The same could be relevant to other materials too and lead to novel applications.

Scanning electron microscopy images

Figure 1. Scanning electron microscopy images of Nd-Fe-B HDDR magnet powder composed of nanocrystals of 250 nm. (a) Magnet before the diffusion process with the coercivity 16 kOe, and (b) Magnet after the diffusion process with the Nd-Cu alloy, showing that dark magnet crystals are separated by light-colored Nd enriched phases.



Atom probe tomography of the magnet

Figure 2. Atom probe tomography of the magnet after the diffusion process with the Nd-Cu alloy, showing Nd and Cu enriched layer around the grain boundary. The presence of Nd-enriched layer around 2 nm thick weakens the magnetic coupling between the crystals, thereby improving the coercivity.