Development of new magnet that reduces use of rare-earth element by 30%
Neodymium is an expensive and unstably supplied material, but it is essential for manufacturing rare-earth permanent magnets. In order to develop an Nd-reduced permanent magnet, the content of cerium (Ce), an inexpensive element, was increased, instead of reducing the content of Nd. Until now, with the increased content of Ce, deterioration of the magnetic properties was inevitable. The research team focused on clarifying the reason for and mechanism of the deterioration of the magnetic properties caused by the increased Ce content, and they successfully solved the problem of rare-earth-reduced permanent magnets by controlling the atomic-scale microstructure.
The researchers discovered that unnecessary magnetic particles were formed during the manufacturing process, the underlying reason for the deterioration of the magnetic and microstructural properties of the magnets. They modified the microstructure and enhanced the magnetic properties by preventing the diffusion of atoms so that the formation of unnecessary magnetic particles is suppressed.
The research team applied the melt-spinning method and the hot-deformation method, which have very fast cooling rates compared to the conventional process, to the process of fabricating rare-earth-reduced precursors and final bulk magnets, respectively. As a result, they succeeded in optimizing the microstructure of the magnets by suppressing the formation of unnecessary magnetic particles. In addition, they were able to simultaneously improve the residual magnetization and coercive force, which are the main properties of permanent magnets.