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論文

A Lightweight shape-memory alloy with superior temperature-fluctuation resistance

Song, Y.*; Xu, S.*; 佐藤駿介*; Lee, I.*; Xu, X.*; 大森俊洋*; 長迫実*; 川崎卓郎; 鬼柳亮嗣; Harjo, S.; et al.

Nature, 638, p.965 - 971, 2025/02

https://doi.org/10.1038/s41586-024-08583-7

被引用回数：2 パーセンタイル：92.88(Multidisciplinary Sciences)

In advanced applications like aerospace and space exploration, materials must balance lightness, functionality, and extreme thermal fluctuation resistance. Shape-memory alloys show promise with strength, toughness, and substantial strain recovery due to superelasticity, but maintaining low mass and effective operation at cryogenic temperatures is challenging. We hereby introduce a novel shape-memory alloy that adheres to these stringent criteria. Predominantly composed of Ti and Al with a chemical composition of Ti $_{75.25}$ Al $_{20}$ Cr $_{4.75}$ , this alloy 25 is characterized by a low density (4.3610 $^{3}$ kg/m $^{3}$ ) and a high specific strength (18510 $^{3}$ Pam $^{3}$ /kg) at room temperature, while exhibiting excellent superelasticity. The superelasticity, owing to a reversible stress-induced phase transformation from an ordered body-centered cubic parent phase to an ordered orthorhombic martensite, allows for a recoverable strain exceeding 7%. Remarkably, this functionality persists across a broad range of temperatures, from deep cryogenic 4.2 K to above room temperature, arising from an unconventional temperature dependence of transformation stresses. Below a certain threshold during cooling, the critical transformation stress inversely correlates with temperature. We interpret this behavior from the perspective of a temperature-dependent anomalous lattice instability of the parent phase. This alloy holds potential in everyday appliances requiring flexible strain accommodations, as well as components designed for extreme environmental conditions such as deep space and liquefied gases.

論文

Concurrent neutron imaging and diffraction analysis revealing spatial lithiation phase evolution in an ultra-thick graphite electrode

Strobl, M.*; Baur, M. E.*; Samothrakitis, S.*; Molamud, F.*; Zhang, X.*; Tung, P. K. M.*; Schmidt, S.*; Woracek, R.*; Lee, J.*; 鬼柳亮嗣; et al.

Advanced Energy Materials, p.2405238_1 - 2405238_9, 2025/01

https://doi.org/10.1002/aenm.202405238

Energy-efficient, safe, and reliable Li-ion batteries (LIBs) are required for a wide range of applications. The introduction of ultra-thick graphite anodes, desired for high energy densities, meets limitations in internal electrode transport properties, leading to detrimental consequences. Yet, there is a lack of experimental tools capable of providing a complete view of local processes. Here, a multi-modal measurement approach is introduced, enabling quantitative spatio-temporal observations of Li concentrations and intercalation phases in ultra-thick graphite electrodes. Neutron imaging and diffraction concurrently provide correlated multiscale information from the scale of the cell down to the crystallographic scale. In particular, the evolving formation of the solid electrolyte interphase (SEI), observation of gradients in total lithium content, as well as in the formation of ordered Li $_{x}$ C $_{6}$ phases and trapped lithium are mapped throughout the first charge-discharge cycle of the cell. Different lithiation stages co-exist during charging and discharging; delayed lithiation and delithiation processes are observed in central regions of the electrode, while the SEI formation, potential plating, and dead lithium are predominantly found closer to the interface with the separator. The study emphasizes the potential to investigate Li-ion diffusion and the kinetics of lithiation phase formation in thick electrodes.

論文

Multiple metamagnetic transitions in the helical antiferromagnet CeVGe $_{3}$

Jin, H.*; Choi, E. S.*; Wu, H.-C.*; Curro, N. J.*; 那波和宏*; 佐藤卓*; 鬼柳亮嗣; 大原高志; Klavins, P.*; Taufour, V.*

Physical Review B, 111(3), p.035103_1 - 035103_7, 2025/01

https://doi.org/10.1103/PhysRevB.111.035103

被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

We report on neutron diffraction, magnetoresistance, magnetization and magnetic torque measurements under high magnetic field in the helical antiferromagnet CeVGe $_{3}$ . This compound exhibits Kondo lattice coherence and helical antiferromagnetic (AFM) ordering at ambient pressure, similar to the well-studied CeRhIn $_{5}$ . Our measurements reveal that CeVGe $_{3}$ undergoes a magnetic transition from an incommensurate (ICM) AFM state to an up-up-down-down commensurate (CM) AFM structure, followed by a transition to a novel phase at higher fields. A quantum phase transition occurs around 21.3 T. This rich magnetic field phase diagram closely resembles that of CeRhIn $_{5}$ . Furthermore, angle-dependent magnetoresistance measurements reveal that all transitions in CeVGe $_{3}$ occur from the field component along the ab plane. These findings highlight the intricate interplay among exchange interactions, crystal field effects, ground state properties, and crystalline symmetries.

論文

Nonferroelectric phase with loss of cycloidal magnetic structure in Tb $_{0.515}$ Gd $_{0.485}$ Mn $_{2}$ O $_{5}$

石井裕太*; 坂倉輝俊*; 石川喜久*; 鬼柳亮嗣; Lustikova, J.*; 青山拓也*; 大串研也*; 若林裕助*; 木村宏之*; 野田幸男*

Physical Review B, 110(18), p.184404_1 - 184404_7, 2024/11

https://doi.org/10.1103/PhysRevB.110.184404

被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Neutron-scattering measurements were employed to investigate the magnetic ordering in Tb $_{1-x}$ Gd $_{x}$ Mn $_{2}$ O $_{5}$ (x = 0.485) enriched with the $^{160}$ Gd isotope, a member of multiferroic RMn $_{2}$ O $_{5}$ (R = rare-earth element) compounds. This material, at low temperatures, exhibits commensurate magnetic (CM) ordering, which drives electric polarization. Notably, electric polarization diminishes as the temperature decreases further, while the CM ordering persists. Magnetic structure analyses revealed that a cycloidal magnetic structure along the c axis transforms into a sinusoidal-like structure, resulting in the nonferroelectric phase, whereas a collinear magnetic structure in the ab plane exhibits no significant change. The findings suggest that the cycloidal magnetic structure plays a key role in inducing electric polarization in the CM ordering of the present material.

論文

Development of an Fe $^{rm II}$ complex exhibiting intermolecular proton shifting coupled spin transition

Ji, T.*; Su, S.*; Wu, S.*; 堀優太*; 重田育照*; Huang, Y.*; Zheng, W.*; Xu, W.*; Zhang, X.*; 鬼柳亮嗣; et al.

Angewandte Chemie; International Edition, 63(25), p.e202404843_1 - e202404843_6, 2024/04

https://doi.org/10.1002/anie.202404843

被引用回数：0 パーセンタイル：0.00(Chemistry, Multidisciplinary)

In this study, we investigated reversible intermolecular proton shifting (IPS) coupled with spin transition (ST) in a novel Fe $^{rm II}$ complex. The host Fe $^{rm II}$ complex and the guest carboxylic acid anion were connected by intermolecular hydrogen bonds (IHBs). We extended the intramolecular proton transfer coupled ST phenomenon to the intermolecular system. The dynamic phenomenon was confirmed by variable-temperature single-crystal X-ray diffraction, neutron crystallography, and infrared spectroscopy.

論文

Tuning of spin-orbit coupling in chiral molecule-incorporated two-dimensional organic-inorganic hybrid perovskite copper halides with ferromagnetic exchange interactions

谷口耕治*; Huang, P.-J.*; 佐賀山基*; 鬼柳亮嗣; 大石一城*; 鬼頭俊介*; 中村唯我*; 宮坂等*

Physical Review Materials (Internet), 8(2), p.024409_1 - 024409_10, 2024/02

https://doi.org/10.1103/PhysRevMaterials.8.024409

被引用回数：2 パーセンタイル：62.00(Materials Science, Multidisciplinary)

Leveraging the flexible material designability of organic-inorganic hybrid systems, spatial inversion symmetry breaking and spin-orbit coupling (SOC) were simultaneously controlled in a series of two-dimensional organic-inorganic hybrid perovskite (2D-OIHP) copper halides with ferromagnetic exchange interaction (FMI). In chiral molecule-incorporated 2D-OIHP copper halides, an increase in Br component over Cl component at halogen sites leads to systematic variations in magnetic phase diagrams owing to the competition between the FMI and Dzyaloshinskii-Moriya interaction induced by the SOC. The crucial role of noncentrosymmetry in the competition for the magnetic interactions was confirmed by comparing the magnetic phase diagrams of chiral and achiral 2D-OIHP copper bromides.

論文

Development of an iron(II) complex exhibiting thermal- and photoinduced double proton-transfer-coupled spin transition in a short hydrogen bond

中西匠*; 堀優太*; 重田育照*; 佐藤寛泰*; 鬼柳亮嗣; 宗像孝司*; 大原高志; 岡澤厚*; 島田林太郎*; 坂本章*; et al.

Journal of the American Chemical Society, 145(35), p.19177 - 19181, 2023/08

https://doi.org/10.1021/jacs.3c06323

被引用回数：5 パーセンタイル：45.65(Chemistry, Multidisciplinary)

Multiple proton transfer (PT) controllable by external stimuli plays a crucial role in fundamental chemistry, biological activity, and material science. However, in crystalline systems, controlling multiple PT, which results in a distinct protonation state, remains challenging. In this study, we developed a novel tridentate ligand and iron(II) complex with a short hydrogen bond (HB) that exhibits a PT-coupled spin transition (PCST). Single-crystal X-ray and neutron diffraction measurements revealed that the positions of the two protons in the complex can be controlled by temperature and photoirradiation based on the thermal- and photoinduced PCST. The obtained results suggest that designing molecules that form short HBs is a promising approach for developing multiple PT systems in crystals.

論文

Spontaneous topological Hall effect induced by non-coplanar antiferromagnetic order in intercalated van der Waals materials

高木寛貴*; 高木里奈*; 見波将*; 野本拓也*; 大石一城*; 鈴木通人*; 柳有起*; 平山元昭*; Khanh, N.*; 軽部皓介*; et al.

Nature Physics, 19(7), p.961 - 968, 2023/07

https://doi.org/10.1038/s41567-023-02017-3

被引用回数：46 パーセンタイル：98.91(Physics, Multidisciplinary)

In ferromagnets, electric current generally induces a transverse Hall voltage in proportion to the internal magnetization. This effect is frequently used for electrical readout of the spin up and down states. While these properties are usually not expected in antiferromagnets, recent theoretical studies predicted that non-coplanar antiferromagnetic order with finite scalar spin chirality - meaning a solid angle spanned by neighboring spins - can induce a large spontaneous Hall effect even without net magnetization or external magnetic field. This phenomenon, the spontaneous topological Hall effect, can potentially be used for the efficient electrical readout of the antiferromagnetic states, but it has not been experimentally verified due to a lack of appropriate materials hosting such magnetism. Here, we report the discovery of all-in-all-out type non-coplanar antiferromagnetic order in triangular lattice compounds CoTa $_{3}$ S $_{6}$ and CoNb $_{3}$ S $_{6}$ . These compounds are reported to host unconventionally large spontaneous Hall effect despite their vanishingly small net magnetization, and our analysis reveals that it can be explained in terms of the topological Hall effect that originates from the fictitious magnetic field associated with scalar spin chirality. These results indicate that the scalar spin chirality mechanism offers a promising route to the realisation of giant spontaneous Hall response even in compensated antiferromagnets, and highlight intercalated van der Waals magnets as a promising quasi-two-dimensional material platform to enable various nontrivial ways of electrical reading and possible writing of non-coplanar antiferromagnetic domains.

論文

Observation of proton-transfer-coupled spin transition by single-crystal neutron-diffraction measurement

中西匠*; 堀優太*; 重田育照*; 佐藤寛泰*; Wu, S.-Q.*; 鬼柳亮嗣; 宗像孝司*; 大原高志; 佐藤治*

Physical Chemistry Chemical Physics, 25(17), p.12394 - 12400, 2023/05

https://doi.org/10.1039/D3CP00527E

被引用回数：3 パーセンタイル：44.56(Chemistry, Physical)

The application of single-crystal neutron diffraction (SCND) to observe proton-transfer phenomena in crystalline compounds exhibiting unusual protonation states or proton dynamics has garnered significant research interest in recent years. However, proton tautomerism, which results in different protonation states before and after proton transfer, has never been observed using the SCND technique. Thus, to observe the proton tautomerism phenomenon by SCND measurements, we developed an iron(II) complex that forms a large crystal and exhibits a proton-transfer-coupled spin transition (PCST). The presence of the two types of proton tautomers was determined by conventional analysis of the proton position by X-ray crystallography, infrared spectroscopy, and density functional theory calculations. Finally, our results confirmed that proton tautomerism was successfully observed for the first time using variable-temperature SCND measurements.

論文

Incommensurate helimagnetic structure of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ determined by single-crystal neutron diffraction

田中誠也*; 鬼柳亮嗣; 石川喜久*; 天児寧*; 飯山拓*; 二村竜祐*; 丸山建一*; 内海重宣*

Physical Review Materials (Internet), 7(1), p.014403_1 - 014403_11, 2023/01

https://doi.org/10.1103/PhysRevMaterials.7.014403

被引用回数：1 パーセンタイル：11.44(Materials Science, Multidisciplinary)

Sc-substituted hexagonal ferrite Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ has an incommensurate helimagnetic structure. However, the incommensurate helimagnetic structure has not been sufficiently determined, and the mechanism via which the helimagnetism develops has not been studied. Time-of-flight single-crystal neutron diffraction measurements were performed on single-crystal samples of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ with Sc concentrations of x = 0, 0.128, 0.153, and 0.193. The magnetic structure analyses revealed that the helimagnetic structure of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ is a cone type whose base is in the ab plane and height is in the c-axis direction. The magnetic moments of Fe2(4), Fe4(4 $f_{2}$ ), and Fe5(12) are aligned with distinct angles, leading to the helimagnetic structure of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ , and can be explained by assuming that there is an antiferromagnetic superexchange interaction $J_{5}$ between Fe2(4) and Fe5(12) that is negligible in the x = 0 crystal. The shorter bond distance of Fe2-O1 in Sc-rich crystals revealed by the crystal structure analyses enhances the superexchange interaction $J_{5}$ . The relatively strong $J_{5}$ leads to competition among the three superexchange interactions, $J_{3}$ , $J_{4}$ , and $J_{5}$ , resulting in the development of the helimagnetic structure. These findings facilitate the understanding of the essentials of the basic magnetic material BaFe $_{12}$ O $_{19}$ .

論文

Rearrangement of hydrogen bonds in dehydrated raffinose tetrahydrate; A Time-of-flight neutron diffraction study

川崎卓郎; 高橋美和子*; 鬼柳亮嗣; 大原高志

Acta Crystallographica Section C; Structural Chemistry (Internet), 78(12), p.743 - 748, 2022/12

https://doi.org/10.1107/S2053229622010828

被引用回数：0 パーセンタイル：0.00(Chemistry, Multidisciplinary)

Structural changes of the raffinose crystal on dehydration from the pentahydrate to the tetrahydrate were investigated by single-crystal time-of-flight neutron diffraction. It was revealed that during the dehydration, rearrangement occurs in the hydrogen bonds related to the lost water molecule, while the symmetry of the crystal structure is retained. The hydrogen-bonding status of raffinose pentahydrate and tetrahydrate were discussed comprehensively according to Jeffrey's hydrogen-bonding classification. It was shown that water molecules are hydrogen bonded to the surrounding molecules by O-H...O hydrogen bonds and C-H...O hydrogen bonds, and the number of these two types of hydrogen bonds determines the water molecules that are removed by dehydration. The lattice constant c showed a significant decrease on dehydration and further dehydration leads to loss of crystallinity of the raffinose crystals.

論文

Evaluation of detector performances of new thin position-sensitive scintillation detectors for SENJU diffractometer

中村龍也; 藤健太郎; 小泉智克; 鬼柳亮嗣; 大原高志; 海老根守澄; 坂佐井馨

Proceedings of 2022 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room Temperature Semiconductor Detector Conference (2022 IEEE NSS MIC RTSD) (Internet), 2 Pages, 2022/11

https://doi.org/10.1109/NSS/MIC44845.2022.10399279

J-PARC物質・生命科学実験施設に設置されたSENJU回折計用として、新たに薄型の位置敏感シンチレータ中性子検出器を開発した。本検出器は既設のオリジナル検出器と同等の有感面積(256256mm)とピクセル分解能(44mm)を保持しつつ、奥行きは12cm(オリジナルの40%)の薄型へと改良した。製作した6台の検出器はいずれも検出効率60%(2A)、計数均一性5-8%と良好な性能を示した。現在、これらの検出器はビームライン内の回折計に装填されており、数か月の安定動作が確認されている。

論文

Optimization and inference of bin widths for histogramming inelastic neutron scattering spectra

巽一厳; 稲村泰弘; 古府麻衣子; 鬼柳亮嗣; 島崎秀昭*

Journal of Applied Crystallography, 55(3), p.533 - 543, 2022/06

https://doi.org/10.1107/S1600576722003624

被引用回数：0 パーセンタイル：0.00(Chemistry, Multidisciplinary)

神経物理学研究において不均一ポアソン過程に基づく観測データのヒストグラムのビン幅最適化が開発され[Shimazaki & Shinomoto (2007). Neural Comput. 19, 1503-1527]、後継研究[Muto et al. (2019). J. Phys. Soc. Jpn, 88, 044002]はその非弾性中性子散乱データへの応用が提唱された。本研究では、銅の単結晶を用いて異なる条件の飛行時間型計測で得られた非弾性中性子散乱の実験データにこの方法を適用し、その結果の正当性を検証した。与えられたデータにおける統計情報を異なる総カウント数のデータに外挿した結果は、それらの実際のデータでの最適なビン幅を精度よく予測した。最適化したビン幅でのヒストグラムはエネルギーおよび運動量の断面において次の二つの微細スペクトル構造の存在の有無を検視した。(1)フォノンバンドギャップの存在、(2)互いに隣接する複数のフォノンブランチの数。磁気励起の新奇な形態や講師熱伝導度に相関するフォノン状態等、物理や材料科学において重要なスペクトル構造を効果的かつ厳正に観測するのを今回適用した方法は助けることをこれは意味する。

論文

Magnetic phase diagram of helimagnetic Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ (0 x 0.2) hexagonal ferrite

丸山建一*; 田中誠也*; 鬼柳亮嗣; 中尾朗子*; 森山健太郎*; 石川喜久*; 天児寧*; 飯山拓*; 二村竜祐*; 内海重宣*; et al.

Journal of Alloys and Compounds, 892, p.162125_1 - 162125_8, 2022/02

https://doi.org/10.1016/j.jallcom.2021.162125

被引用回数：2 パーセンタイル：10.70(Chemistry, Physical)

Hexagonal ferrite Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ is an important magnetic oxide material in both science and engineering because it exhibits helimagnetism around room temperature (300 K). In this study, the magnetic phase diagram of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ consisting of ferri-, heli-, antiferro-, and paramagnetic phases has been completed through magnetization and neutron diffraction measurements. The magnetic phase transition temperature to paramagnetism decreases with the increase in x, and the temperature at which the magnetization reaches a maximum, which corresponds to the magnetic phase transition from heli- to ferrimagnetism, is determined for low x crystals. The temperatures at which helimagnetism appears are precisely determined by observing the magnetic satellite reflection peaks in neutron diffraction at various temperatures, which characterize helimagnetism. Based on these results, the magnetic phase diagram of the Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ system is constructed in the T-x plane. Helimagnetism appears at x 0.06, and magnetism with antiferromagnetic components appears as the extension phase of helimagnetism at x 0.19 through the coexistence region. The turn angle $phi_{0}$ of the helix for each x crystal is calculated from the relationship, $phi_{0} = 2pidelta$ , where is the incommensurability. The turn angle $phi_{0}$ decreases with the increase in temperature for the same x crystal, and increases with the increase in x at the same temperature. Furthermore, it is found that there are clear thresholds at which $phi_{0}$ cannot take values between 0 $^{circ}$ < $phi_{0}$ < 90 $^{circ}$ and 170 $^{circ}$ < $phi_{0}$ < 180 $^{circ}$ .

論文

Two-dimensional scintillation neutron detectors for the extension of SENJU diffractometer

中村龍也; 藤健太郎; 小泉智克; 鬼柳亮嗣; 大原高志; 海老根守澄; 坂佐井馨

Proceedings of 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC 2020), Vol.1, p.483 - 484, 2021/09

https://doi.org/10.1109/NSS/MIC42677.2020.9507813

J-PARCに設置されたSENJU回折計に増設するためのコンパクトな2次元シンチレータ中性子検出器を開発した。本検出器では設置部の空間制約に対応するため、オリジナルと同様の有感面積(256256mm)とピクセル分解能(44mm)を保持しつつ、奥行き170mm(従来比40%減)へ再設計し製作した。また、新開発のコンパレータボードを装填することでPMT印加電圧の低減と計数均一性を改善した。4台製作した増設用検出器はいずれも検出効率50-60% (2)、 $^{60}$ Coガンマ感度110 $^{-5}$ 、計数均一性3-6%であり良好な性能を有することを確認した。

論文

Charge-density-wave order and multiple magnetic transitions in divalent europium compound EuAl

金子耕士; 川崎卓郎; 仲村愛*; 宗像孝司*; 中尾朗子*; 花島隆泰*; 鬼柳亮嗣; 大原高志; 辺土正人*; 仲間隆男*; et al.

Journal of the Physical Society of Japan, 90(6), p.064704_1 - 064704_6, 2021/06

https://doi.org/10.7566/JPSJ.90.064704

被引用回数：50 パーセンタイル：95.05(Physics, Multidisciplinary)

Multiple transition phenomena in divalent Eu compound EuAl with the tetragonal structure were investigated via single crystal time-of-flight neutron Laue technique. At 30 K below a charge-density-wave (CDW) transition, superlattice peaks emerge near nuclear Bragg peaks described by an ordering vector $q_{rm CDW}$ = (0 0 ${delta}_c$ ). In contrast, magnetic peaks appear at $q_2 = ({delta}_2 {delta}_2 0)$ with ${delta}_2$ = 0.09 below $T_{N1}$ = 15.4 K, and moves to $q_1 = ({delta}_1 0 0)$ with ${delta}_1$ = 0.19 below $T_{N3}$ =12.2 K, whereas no distinct change in the magnetic Bragg peak was detected at $T_{N2}$ and $T_{N4}$ . The structural modification with $q_{rm CDW}$ is characterized by an absence of the superlattice peak in (0 0 ). Considering an absence of splitting in magnetic peaks along , the structural transition is mainly ascribed to a displacement of Al ions within the tetragonal -plane. Complex incommensurate magnetic transitions are in stark contrast to a simple collinear commensurate structure in isovalent EuGa. This could stem from incompatible electronic structures with the CDW transition between two compounds.

論文

Competing spin modulations in the magnetically frustrated semimetal EuCuSb

高橋英史*; 青野快*; 南部雄亮*; 鬼柳亮嗣; 野本拓也*; 坂野昌人*; 石坂香子*; 有田亮太郎*; 石渡晋太郎*

Physical Review B, 102(17), p.174425_1 - 174425_6, 2020/11

https://doi.org/10.1103/PhysRevB.102.174425

被引用回数：17 パーセンタイル：64.14(Materials Science, Multidisciplinary)

六方晶層状構造を有する遍歴磁石EuCuSbの競合する磁気基底状態を、単結晶試料を用いた磁化、抵抗率および中性子回折によって測定した。EuCuSbは、バンド計算と角度分解光電子分光法によって3次元の半金属バンド構造を持つことがわかっており、常磁性状態でのほぼ等方性の金属伝導率と一致している。一方、反強磁性転移温度( $_{rm N1}$ =8.5K)以下では、特にc軸に沿った抵抗率が大幅な増加を示し、伝導電子に結合した異方的な磁気秩序の出現を示唆する。中性子回折実験の結果、各層内で強磁性的に秩序化するEuスピンが、 $_{rm N1}$ 以下ではc軸に沿ってコリニアに変調し、 $_{rm N2}$ (6K)以下では、部分的にらせんスピン変調が出現することがわかった。異常な磁気抵抗の観測に基づき、中心対称構造を持つフラストレーションのあるHeisenberg-likeなスピン系に固有の基底状態の競合する性質について議論する。

論文

Flux growth and magnetic properties of helimagnetic hexagonal ferrite Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ single crystals

内海重宣*; 田中誠也*; 丸山建一*; 天児寧*; 鬼柳亮嗣; 中尾朗子*; 森山健太郎*; 石川喜久*; 他9名*

ACS Omega (Internet), 5(38), p.24890 - 24897, 2020/09

https://doi.org/10.1021/acsomega.0c03671

被引用回数：5 パーセンタイル：20.39(Chemistry, Multidisciplinary)

六方晶フェライトBa(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ の磁気構造を解明し、さらなる応用開発を進めるためには、大型の高品質な単結晶を育成することが重要な第一歩である。本研究では、Na $_{2}$ O-Fe $_{2}$ O $_{3}$ フラックスを使用した自発結晶化法によって、さまざまなSc濃度のBa(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ 単結晶の育成に成功した。得られた結晶は、高品質の単相Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ であることがX線回折と元素分析により確認され、 = 0.128結晶の77Kの磁化測定では、ヘリマグネティックな挙動を示すことがわかった。=0.128結晶の中性子回折測定の結果、211K以下で磁気衛星反射が確認され、Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ がヘリ磁性物質であることが確認された。

論文

Successive phase transitions in $R_{3}$ Ir $_{4}$ Sn $_{13}$ (: La and Ce) investigated using neutron and X-ray diffraction

中里晟也*; 岩佐和晃*; 橋本大輔*; 塩澤真未*; 桑原慶太郎*; 中尾裕則*; 佐賀山基*; 石角元志*; 大原高志; 中尾朗子*; et al.

JPS Conference Proceedings (Internet), 30, p.011128_1 - 011128_6, 2020/03

https://doi.org/10.7566/JPSCP.30.011128

Successive phase transitions of $R_{3}$ Ir $_{4}$ Sn $_{13}$ (: La and Ce) were studied using neutron and X-ray diffraction techniques. A semimetal Ce $_{3}$ Ir $_{4}$ Sn $_{13}$ undergoes three phase transitions: an antiferromagnetic ordering characterized by a propagation vector $q_{rm M}$ = (1/2, 1/2, 2/5) below 0.6 K, a structural transformation with $q_{rm S2}$ = (1/4, 1/4, 1/4) at 2.0 K, and another structural transformation with $q_{rm S1}$ = (1/2, 1/2, 0) above room temperature. La $_{3}$ Ir $_{4}$ Sn $_{13}$ was confirmed to be a superconductor below 2.5 K under the $q_{rm S1}$ = (1/2, 1/2, 0) structure that also appears above room temperature.

論文

Multi-step magnetic transitions in EuNiIn

池田修悟*; 金子耕士; 田中佑季*; 川崎卓郎; 花島隆泰*; 宗像孝司*; 中尾朗子*; 鬼柳亮嗣; 大原高志; 望月健生*; et al.

Journal of the Physical Society of Japan, 89(1), p.014707_1 - 014707_7, 2020/01

https://doi.org/10.7566/JPSJ.89.014707

被引用回数：2 パーセンタイル：18.11(Physics, Multidisciplinary)

Magnetism in EuNiIn has been studied by specific heat, magnetic susceptibility, magnetization, $^{151}$ Eu Mssbauer spectroscopy, and neutron diffraction experiments. The specific heat shows two magnetic transitions at $T_{rm N1}$ and $T_{rm N2}$ at zero magnetic field. An antiferromagnetic ground state of EuNiIn has a uniaxial magnetic anisotropy along the b-axis, revealed by the magnetic susceptibility and the Mssbauer spectroscopy. Single crystal neutron diffraction experiments clarify that this antiferromagnetic structure in the ground state is characterized by the commensurate propagation vector = (1/2, 1/2, 1/2) which reveals no distinct anomaly at $T_{rm N2}$ . The magnetization curve along the b-axis at 2 K shows four successive magnetic field-induced transitions up to 50 kOe and, reaches 7 ${mu}_{rm B}$ /f.u. above 190 kOe, The magnetic phase diagram in EuNiIn has unique characteristics with five magnetic states in low magnetic field.