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論文

Observation of field-induced single-ion magnetic anisotropy in a multiorbital Kondo alloy (Lu,Yb)RhZn $_{20}$

北澤崇文; 池田陽一*; 榊原俊郎*; 松尾晶*; 清水悠晴*; 徳永陽; 芳賀芳範; 金道浩一*; 南部雄亮*; 池内和彦*; et al.

Physical Review B, 108(8), p.085105_1 - 085105_7, 2023/08

https://doi.org/10.1103/PhysRevB.108.085105

We demonstrate field-induced single-ion magnetic anisotropy resulting from the multiorbital Kondo effect on diluted ytterbium alloy (Lu $_{1-x}$ Yb)RhZn $_{20}$ . Single-ion anisotropic metamagnetic behavior is revealed in low-temperature regions where the local Fermi-liquid state is formed. Specific heat, low-field magnetic susceptibility, and resistivity indicate reproduction of the ground-state properties by the SU( = 8) Kondo model with a relatively large - hybridization of $T_{rm K}$ = 60.9 K. Dynamical susceptibility measurements on YbRhZn $_{20}$ support realizing multiorbital Kondo ground state in (Lu $_{1-x}$ Yb)RhZn $_{20}$ . The single-ion magnetic anisotropy becomes evident above 5 T, which is lower than the isotropic Kondo crossover field of 22.7 T, verifying blurred low-lying crystal field states through the multiorbital Kondo effect.

論文

A Storm-induced flood and associated nearshore dispersal of the river-derived suspended $^{137}$ Cs

内山雄介*; 徳永夏樹*; 東晃平*; 上平雄基; 津旨大輔*; 岩崎理樹*; 山田正俊*; 立田穣*; 石丸隆*; 伊藤友加里*; et al.

Science of the Total Environment, 816, p.151573_1 - 151573_13, 2022/04

https://doi.org/10.1016/j.scitotenv.2021.151573

被引用回数：5 パーセンタイル：74.58(Environmental Sciences)

福島県新田川を対象に、台風201326号に伴う出水イベントに着目し、台風通過直後に実施された海底堆積調査結果と、高解像度海洋モデルを併用することによって新田川起源の懸濁態放射性核種の海底での堆積状況を評価した。数値モデルによる底面せん断応力、残差流による懸濁質輸送、局所的土砂収支に対応する侵食・堆積パターンは、現地観測結果を定性的によく説明しており、モデルの妥当性を示すとともに観測による懸濁態 $^{137}$ Cs分布パターンの形成機構について明確な解釈を与えた。

論文

Magnetically induced electric polarization in Ba $_{3}$ Fe $_{2}$ O $_{5}$ Cl $_{2}$ with tunable direction in three dimensions

阿部伸行*; 塩澤俊介*; 松浦慧介*; 佐賀山基*; 中尾朗子*; 大原高志; 徳永祐介*; 有馬孝尚*

Physical Review B, 101(18), p.180407_1 - 180407_5, 2020/05

https://doi.org/10.1103/PhysRevB.101.180407

被引用回数：2 パーセンタイル：15.45(Materials Science, Multidisciplinary)

The correlation between magnetism and electric polarization in a chiral insulating magnet Ba $_{3}$ Fe $_{2}$ O $_{5}$ Cl $_{2}$ has been investigated. The temperature dependence of magnetic susceptibility shows an anomaly at 564 K, suggesting the onset of antiferromagnetic order of Fe $^{3+}$ moments. Electric polarization appears in a magnetic field below TN due to the spin-direction-dependent metal-ligand hybridization. The direction of the electric polarization can be controlled in three-dimensional space by changing the direction of an external magnetic field. This compound also shows an antiferromagnetic-to-weak-ferromagnetic transition accompanied by a structural phase transition at 140 K.

論文

国際核融合エネルギー研究センターの高性能計算機システムHeliosを利用した国内シミュレーション研究プロジェクトの進展

石澤明宏*; 井戸村泰宏; 今寺賢志*; 糟谷直宏*; 菅野龍太郎*; 佐竹真介*; 龍野智哉*; 仲田資季*; 沼波政倫*; 前山伸也*; et al.

プラズマ・核融合学会誌, 92(3), p.157 - 210, 2016/03

http://www.jspf.or.jp/Journal/PDF_JSPF/jspf2016_03/jspf2016_03-157.pdf

幅広いアプローチ協定に基づいて国際核融合エネルギー研究センター(IFERC)の計算機シミュレーションセンター(CSC)に設置された高性能計算機システムHeliosは、2012年1月に運用を開始し、日欧の磁気核融合シミュレーション研究に供用され、高い利用率の実績を示すとともに、炉心プラズマ物理から炉材料・炉工学にわたる広い分野で多くの研究成果に貢献している。本プロジェクトレビューの目的は、国内の大学や研究機関においてHeliosを利用して進められているシミュレーション研究プロジェクトとその成果を一望するとともに、今後予想される研究の進展を紹介することである。はじめにIFERC-CSCの概要を示した後、各研究プロジェクト毎にその目的、用いられる計算手法、これまでの研究成果、そして今後必要とされる計算を紹介する。

論文

Magnetoelectric coupling in the honeycomb antiferromagnet Co $_{4}$ Nb $_{2}$ O $_{9}$

Khanh, N. D.*; 阿部伸行*; 佐賀山基*; 中尾朗子*; 花島隆泰*; 鬼柳亮嗣; 徳永祐介*; 有馬孝尚*

Physical Review B, 93(7), p.075117_1 - 075117_6, 2016/02

https://doi.org/10.1103/PhysRevB.93.075117

被引用回数：94 パーセンタイル：95.25(Materials Science, Multidisciplinary)

The magnetic structure and magnetoelectric effect have been investigated for single crystals of the antiferromagnet Co $_{4}$ Nb $_{2}$ O $_{9}$ . Single-crystal neutron diffraction and magnetic susceptibility measurement have revealed that the magnetic structure is different from a collinear arrangement with spin parallel to the trigonal axis as proposed previously. Co $^{2+}$ magnetic moments are found to be almost lying in the basal plane, which lowers the magnetic symmetry to with the propagation vector = 0. Associated with the magnetic phase transition, a sharp anomaly in the dielectric constant and displacement current indicate the appearance of the magnetoelectric below Neel temperature TN with a large coupling constant up to 30 ps/m. The existence of off-diagonal components in a magnetoelectric tensor indicate the formation of ferrotoroidic order in Co $_{4}$ Nb $_{2}$ O $_{9}$ . Such a magnetoelectric effect can be ascribed to the reduction of symmetry caused by simple antiferromagnetic order in a honeycomb network.

論文

Emergent phenomena in perovskite-type manganites

田口康二郎*; 酒井英明*; 奥山大輔*; 石渡晋太郎*; 藤岡淳*; 福田竜生; 橋爪大輔*; 賀川史敬*; 高橋陽太郎*; 島野亮*; et al.

Physica B; Condensed Matter, 407(11), p.1685 - 1688, 2012/06

https://doi.org/10.1016/j.physb.2012.01.006

被引用回数：5 パーセンタイル：24.52(Physics, Condensed Matter)

Perovskite-type manganites exhibit various interesting phenomena arising from complex interplay among spin, charge, orbital, and lattice degrees of freedom. As the respective examples, perovskite-type YMnO and Sr $_{1-x}$ BaMnO are discussed. In the YMnO, the ferroelectric lattice distortion associated with the -type spin order is observed for the first time. Displacement-type ferroelectricity with off-center magnetic ions is discovered for Sr $_{0.5}$ Ba $_{0.5}$ MnO, which shows both large polarization value and strong coupling between ferroelectricity and magnetism.

論文

Multiferroic -type hexaferrites with a room-temperature conical state and magnetically controllable spin helicity

徳永祐介*; 金子良夫*; 奥山大輔*; 石渡晋太郎*; 有馬孝尚*; 脇本秀一; 加倉井和久; 田口康二郎*; 十倉好紀*

Physical Review Letters, 105(25), p.257201_1 - 257201_4, 2010/12

https://doi.org/10.1103/PhysRevLett.105.257201

被引用回数：260 パーセンタイル：98.34(Physics, Multidisciplinary)

Magnetic and magnetoelectric (ME) properties have been studied for single crystals of Sc-doped -type barium hexaferrites. Magnetization () and neutron diffraction measurements revealed that by tuning Sc concentration a longitudinal conical state is stabilized up to above room temperatures. ME measurements have shown that a transverse magnetic field () can induce electric polarization () at lower temperatures and that the spin helicity is nonvolatile and endurable up to near the conical magnetic transition temperature.

口頭

Neutron scattering activities on multiferroic systems; Neutron diffraction experiments on hexaferrites

加倉井和久; 脇本秀一; 石渡晋太郎*; 奥山大輔*; 西正和*; 徳永祐介*; 有馬孝尚*; 田口康二郎*; 十倉好紀*

no journal, ,

The discovery of magnetoelectric (ME) effects caused by a cycloidal spin order has initiated an intense research on new class of ME materials. Among them one interesting class of materials is the hexaferrites such as Y-type (A $_{2}$ Me $_{2}$ Fe $_{12}$ O $_{22}$ : Me=transition metal), M-type (AFe $_{12}$ O $_{19}$ : A=Pb, Ca, Sr, Ba, etc.), where types of elementary blocks and their stacking order are different. These materials show a variety of complex magnetic ordering. In this presentation recent neutron diffraction experiments on multiferroic hexaferrites performed at the JRR-3 Neutron Science Facility of Japan Atomic Energy Agency (JAEA) are reported.

口頭

単結晶中性子回折による室温マルチフェロイック・ヘキサフェライトBaSrCo $_{2}$ Fe $_{11}$ AlO $_{22}$ の磁気秩序の研究

中島多朗*; 徳永祐介*; 松田雅昌*; Dissanayake, S.*; Fernandez-Baca, J. A.*; 加倉井和久; 田口康二郎*; 十倉好紀*; 有馬孝尚*

no journal, ,

室温マルチフェロイック・ヘキサフェライトBaSrCo $_{2}$ Fe $_{11}$ AlO $_{22}$ における磁気秩序を磁化・分極測定及び中性子散乱実験により明らかにした。基底状態の磁気構造はc軸方向にコーン軸を持つAlternating Longitudinal Conical (ALC)磁気構造であり、これにc軸垂直方向の磁場を加えると、格子整合な磁気伝播波数を持つノンコリニアな磁気相が現れることが分かった。

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