Research Abstract
人工的に作製したレア・アースフリー天然隕石磁石
Artificially produced rare-earth free cosmic magnet
2015年11月16日 Scientific Reports 5 : 16627 doi: 10.1038/srep16627
我々は、天然隕石よりも高い規則度で化学的に規則化した硬磁性L10-FeNi相を人工的に作製した。本合金設計により、作製時間は天然隕石の数億年から300時間未満に短縮された。作製したL10-FeNi相には、4回の回転対称性の110超格子反射と高い化学的規則度パラメーター（S≧ 0.8）が電子回折で検出された。磁化反転には、3.5 kOe以上の磁場が必要であった。本実験結果と計算機シミュレーション結果から、以下で列挙されるアモルファス状態に関連する3つの要因、すなわち、結晶化時の低温での構成原子の高い拡散速度、L10相の大きな析出駆動力、および、L10クラスターが存在する可能性、によって、規則相が形成されることが示唆される。本合金はレア・アース元素を含んでおらず、しかもこの作製手法が量産に適しているため、本結果は、次世代硬磁性材料の開発における鉱物資源枯渇問題を解決できる。
Akihiro Makino, Parmanand Sharma, Kazuhisa Sato, Akira Takeuchi, Yan Zhang & Kana Takenaka
Corresponding Authors
Chemically ordered hard magnetic L10-FeNi phase of higher grade than cosmic meteorites is produced artificially. Present alloy design shortens the formation time from hundreds of millions of years for natural meteorites to less than 300 hours. Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S 
0.8) for the developed L10-FeNi phase. The magnetic field of more than 3.5 kOe is required for the switching of magnetization. Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase, and the possible presence of L10 clusters. Present results can resolve mineral exhaustion issues in the development of next-generation hard magnetic materials because the alloys are free from rare-earth elements, and the technique is well suited for mass production.
0.8) for the developed L10-FeNi phase. The magnetic field of more than 3.5 kOe is required for the switching of magnetization. Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase, and the possible presence of L10 clusters. Present results can resolve mineral exhaustion issues in the development of next-generation hard magnetic materials because the alloys are free from rare-earth elements, and the technique is well suited for mass production. 
