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Magnetic Structrure of Nd2Fe14B

The 58th Annual Conference on Magnetism and Magnetic Materials (MMM)

T.Yoshioka ( Tohoku Univ )
H.Tsuchiura ( Tohoku Univ )
N.Miura ( Tohoku Univ )
P.Novak ( ASCR )

Abstract

To reveal the coercivity mechanism of sintered Nd-Fe-B magnets is cruciallyimportant from not only scientific interests but also the viewpoint of sustainabletechnology.
To this end, we need to clarify the magnetic propertiesof the crystalline Nd2Fe14B as the main phase of Nd-Fe-B from microscopicperspective.
One of the authors and his coworkers have estimated the leadingcrystal field coefficient A20 of Nd ions exposed on the (001) surface ofthe crystalline Nd2Fe14B based on first-principles calculations, and havefound that they exhibit c-plane magnetic anisotropy, resulting in a reductionof the coercivity of a single Nd2Fe14B grain by half of the anisotropy fieldHK.
For deeper understanding of the magnetic properties, it is highly desirableto obtain reliable theoretical results for higher Alm and the exchangecoupling between Fe-Fe and Nd-Fe, because the experimental determinationof such parameters requires a multi-parameter fit to the experimental data inwhich there is an inevitable ambiguity.
Thus in this paper, we report suchphysical quantities by using first-principles calculations.
Table I shows thecrystal field coefficients A20, A2-2, A40, A4-2, A44 at the Nd sites inNd2Fe14B.
We find that the values of A2-2 and A40 are comparable to thatof A20.
We also report the crystal field coefficients Alm of RE ions inPr2Fe14B and Dy2Fe14B, and also in Ce2Fe14B for comparison, to obtainfurther insight into the magnetic anisotropy and coercivity of Nd2Fe14Bmagnets.


研究活動

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