Efficiently controlling crystallization and magnetic properties of nanostructured Nd-Ce-Fe-B ribbons via electron beam exposure.

Electron beam exposure (EBE) has been implemented to synthesize Nd-Ce-Fe-B-based nanostructured magnetic materials with controllable morphology and tunable magnetic properties. Greatly reduced crystallization time of amorphous ribbons to about 0.1 s is achieved, which is by far the most effective method due to the effect of an extremely high heating rate. The extremely high heating rate gives rise to a huge temperature gradient in the annealed ribbons leading to platelet-like grains due to the oriented nucleation and growth under quasi-static thermal stress. It was found that the size and shape of the grains can be finely controlled by the beam current intensity. A coercivity as high as 12.9 kOe, and a maximum energy product as high as 15.4 MGOe are obtained in pure (Nd 0.8 Ce 0.2) 12.2 Fe 81.6 B 6.2 ribbons exposed to a beam current of 0.4 mA, without doping any other heavy rare earth or coercivity enhancement elements. A single magnetic domain covering many grains was observed by the Lorentz transmission microscope (LTEM). It was found that the improvement of the magnetic performance has a deep correlation with the achievement of a single domain structure. Our results demonstrate that EBE shows great advantages in preparing the high coercivity Ce-substituted Nd 2 Fe 14 B magnets due to higher efficiency and higher controllability than conventional furnace annealing. Image 1 [ABSTRACT FROM AUTHOR]