| 研究実績の概要 |
Considerable efforts have been devoted to increasing coercivity (Hc) of SmFe12 (ThMn12, I4/mmm) based permanent magnet materials while retaining sufficiently large remanent magnetization (Mr). In general, the achievable Hc is determined by multiple factors, including the intrinsic material properties and microstructure of the materials. To push the current magnetic performance limit of SmFe12-based permanent magnet materials, these factors should be considered comprehensively and optimized synergistically.
Herein I have succeeded in preparing (Sm,Zr)(Fe,Co,Ti)12 well-defined particles with ever-larger Hc and Mr based on precise control over their crystallinity and microstructure using chemical synthesis. Synthesized (Sm,Zr)(Fe,Co,Ti)12 particles have high crystallinity and diverse surface from Sm-enriched to Ti-enriched and depleted surface. The most important achievement was to turn out that the inevitable formation of magnetically-soft surface (SmFex compounds) is responsible for very low Hc and the refined surfaces resulted in intriguing Hc. As a result, Hc and Mr values of (Sm,Zr)(Fe,Co,Ti)12 isotropic powders at 300 K were as large as 1.6 T and 1.2 T, respectively, the world's highest performance for SmFe12-based permanent magnet materials. This result is a breakthrough in the development of SmFe12-based permanent magnet materials, opening a new era of permanent magnets.
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