ホーム > 研究活動 > 口頭発表(2019) > Theoretical study on the electronic states and finite temperture magnetic properties ofSm2fe17Nx

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Theoretical study on the electronic states and finite temperture magnetic properties ofSm2fe17Nx

64th Annual Conference on Magnetism and Magnetic Materials

Shogo Yamashita(Tohoku University),Hiroki Tsuchiura(Tohoku University), TakuyaYoshioka(Tohoku University)

Abstract

The Sm2Fe17Nx nitrides have unusual anisotropic magnetic properties. It is well known that the systemat x=3 exhibits strong uniaxial magnetocrystal- line anisotropy, which is higher than that of Nd2Fe14B.On the other hand, the system at x=0, that is binary Sm2Fe17, has weak planar anisotropy. A first-principles study in early days showed that the Sm local anisotropy in Sm2Fe17 is weak but strongenough to overcome that of the Fe sublattice when the Sm is treated as a trivalent ion in thecalculations [1]. Another recent ab-initio study based on the KKR method has claimed that the Sm ionsmay have a divalent electronic configuration [2]. Motivated by these backgrounds, in this contribution,we examine the magnetocrystalline anisot- ropy of the Sm2Fe17Nx systems assuming the Sm3+ orSm2+ configuration based on first-principles calculations. Furthermore, we construct an effec- tive spinmodel to describe the finite temperature magnetic properties of these systems based on the informationsuch as crystal field parameters obtained in the first-principles way. First of all, we calculate the crystalfield parameters, the leading term of which is A20<r2>=-171 K (-8.85 K) and -554 K (-686 K) for Sm3+(Sm2+) ion in Sm2Fe17 and Sm2Fe17N3, respectively. These values are all negative, which indicatesthat the Sm ions has local uniaxial anisotropy. However, its amplitude is very small when we assume thedivalent configuration for the Sm ions in Sm2Fe17. Fig. 1 and 2 show the temperature dependence of themagnetization curves along the c-axis and (100) direction of these systems obtained by using theeffective spin model. We can see that the experimental result is well described for Sm2Fe17N3 but noteven qualitatively for Sm2Fe17 when we assume the Sm3+ configuration for the Sm. Instead, we findthat the spin model based on the Sm2+ ions can give a qualitatively consistent result with theexperimental one. These results imply that the valency of the Sm ions in Sm2Fe17Nx systems can bestrongly affected by nitrogenation processes.






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