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研究活動

Computational exploration of strong permanent magnet compounds

MMM2018(Osaka)

2018年11月2日(金)

Takashi Miyake

Abstract

Modern strong magnets are rare-earth magnets in which high saturation magnetization andhigh Curie temperature come from transition-metal 3d electrons, and strongmagnetorcystalline anisotropy originates from rare-earth 4f electrons [1]. There are varioustypes of crystal structures and chemical composition, and exploration of a new magnetcompound is a hot topic. Among them, RFe12-type compounds with the ThMn12 structure areattracting renewed interest because of their high iron content. Recently synthesizedNdFe12Nx film has higher saturation magnetization and anisotropy field than Nd2Fe14B,although its bulk phase is thermodynamically unstable. I will present a first-principles study onthe effect of element substitution on magnetism and structural stability. I will also discuss howmachine learning accelerates magnetic-materials discovery. Application to the Curietemperature of RFe12-type compounds shows that Bayesian optimization offers an efficientway to optimize chemical composition of magnet compounds. Kernel ridge regression usingorbital-field matrix as a descriptor reproduces the magnetic moment and formation energy ofthousands of transition-metal compounds in reasonable accuracy [2], which can be utilized forvirtual screening of new magnetic compounds. Bayesian optimization approach to crystalstructure prediction is also presented [3].
[1] Takashi Miyake and Hisazumi Akai, J. Phys. Soc. Jpn. 87, 041009 (2018).
[2] T.L. Pham et al., Sci. Tech. Adv. Mater. 18, 756 (2017).
[3] T. Yamashita et al., Phys. Rev. Mater. 2, 013803 (2018).


研究活動

文部科学省

文部科学省
元素戦略プロジェクト(活動紹介)
NIMS磁石パートナーシップ

元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合