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論文

Spin caloritronics in metallic superlattices

関剛斎*; 内田健一*; 高梨弘毅

Journal of Physics; Condensed Matter, 36(33), p.333001_1 - 333001_11, 2024/05

https://doi.org/10.1088/1361-648X/ad4761

Spin caloritronics, a research field studying on the interconversion between a charge current (J $_{rm c}$ ) and a heat current (J $_{rm q}$ ) mediated by a spin current (J $_{rm s}$ ) and/or magnetization (M), has attracted much attention not only for academic interest but also for practical applications. Newly discovered spin-caloritronic phenomena such as the spin Seebeck effect (SSE) have stimulated the renewed interest in the thermoelectric phenomena of a magnet, which have been known for a long time, e.g. the anomalous Nernst effect (ANE). These spin-caloritronic phenomena involving the SSE and the ANE have provided with a new direction for thermoelectric conversion exploiting J $_{rm s}$ and/or M. Importantly, the symmetry of ANE allows the thermoelectric conversion in the transverse configuration between J $_{rm q}$ and J $_{rm c}$ . Although the transverse configuration is totally different from the conventional longitudinal configuration based on the Seebeck effect and has many advantages, we are still facing several issues that need to be solved before developing practical applications. The primal issue is the improvement of conversion efficiency. In the case of ANE-based applications, a material with a large anomalous Nernst coefficient (S $_{rm ANE}$ ) is the key for solving the issue. This review article introduces the increase of S $_{rm ANE}$ can be achieved by forming superlattice structures, which has been demonstrated for several kinds of materials combinations. The overall picture of studies on spin caloritronics is first surveyed. Then, we mention the pioneering work on the transverse thermoelectric conversion in superlattice structures, which was performed using Fe-based metallic superlattices, and show the recent studies for the Ni-based metallic superlattices and the ordered alloy-based metallic superlattices.

論文

Field-induced insulator-metal transition in EuTe

竹内徹也*; 本多史憲*; 青木大*; 芳賀芳範; 木田孝則*; 鳴海康雄*; 萩原政幸*; 金道浩一*; 軽部皓介*; 播磨尚朝*; et al.

Journal of the Physical Society of Japan, 93(4), p.044708_1 - 044708_10, 2024/04

https://doi.org/10.7566/JPSJ.93.044708

Electrical and magnetic properties of divalent europium antiferromagnet EuTe are studied on single crystals grown from Te-flux method. Antiferromagnetism occurs at 11 K with an insulating ground state. Application of magnetic field induces a sudden resistance drop leading to a phase transition to metallic state. Energy band calculations reveal the appearance of a Fermi surface pocket with Te-5p character induced by the polarized Eu moments.

論文

Overview of development program for engineering scale extraction chromatography MA(III) recovery system

渡部創; 高畠容子; 長谷川健太; 後藤一郎*; 宮崎康典; 渡部雅之; 佐野雄一; 竹内正行

Mechanical Engineering Journal (Internet), 11(2), p.23-00461_1 - 23-00461_10, 2024/04

https://doi.org/10.1299/mej.23-00461

Japan Atomic Energy Agency is developing extraction chromatography technology to recover MA(III) from spent nuclear fuel. Developments in the extraction chromatography system especially focusing on safety and stable operation are required for practical application of the technology. This paper discusses the main tasks that have to be challenged preferentially based on achievements obtained by previous studies and potential MA(III) recovery process flow.

論文

Magnetic layer thickness influence on magnetoelastic properties anisotropy in Co $_{2}$ Fe $_{0.4}$ Mn $_{0.6}$ Si heusler alloy thin films

Nabialek, A.*; Chumak, O.*; 関剛斎*; 高梨弘毅; Baczewski, L. T.*; Szymczak, H.*

IEEE Transactions on Magnetics, 59(11), p.2501405_1 - 2501405_5, 2023/11

https://doi.org/10.1109/TMAG.2023.3287324

The anisotropic magnetoelastic (ME) properties of epitaxial Co $_{2}$ Fe $_{0.4}$ Mn $_{0.6}$ Si(CFMS) Heusler alloy thin films with thicknesses ranging from 8 to 100 nm were investigated using the strain-modulated ferromagnetic resonance (SMFMR) technique. The calculation of the first cubic magnetocrystalline (MC) constant $_{1}$ and the two cubic ME constants $_{1}$ and $_{2}$ was carried out assuming the cubic symmetry of the magnetic layer. A significant negative perpendicular MC anisotropy, of the order of 10 $^{5}$ J/m $^{3}$ , was also observed. The investigated parameters were found to be dependent on the thickness of the magnetic layer. The thinnest magnetic layers showed the strongest cubic MC anisotropy and the weakest anisotropy of ME properties. These findings highlight the importance of considering the magnetic layer thickness when evaluating the anisotropy in the ME properties of Heusler alloy thin films.

論文

Antiferromagnetic films and their applications

廣畑貴文*; Lloyd, D. C.*; 窪田崇秀*; 関剛斎*; 高梨弘毅; 介川裕章*; Wen, Z.*; 三谷誠司*; 小泉洸生*

IEEE Access, 11, p.117443 - 117459, 2023/10

https://doi.org/10.1109/ACCESS.2023.3326448

Spintronic devices are expected to replace the recent nanoelectronic memories and sensors due to their efficiency in energy consumption and functionality with scalability. To date, spintronic devices, namely magnetoresistive junctions, employ ferromagnetic materials by storing information bits as their magnetization directions. However, in order to achieve further miniaturization with maintaining and/or improving their efficiency and functionality, new materials development is required: 1) increase in spin polarization of a ferromagnet or 2) replacement of a ferromagnet by an antiferromagnet. Antiferromagnetic materials have been used to induce an exchange bias to the neighboring ferromagnet but they have recently been found to demonstrate a 100% spin-polarized electrical current, up to THz oscillation and topological effects. In this review, the recent development of three types of antiferromagnets is summarized with offering their future perspectives towards device applications.

報告書

SPring-8 JAEA専用ビームラインBL22XUの設計

塩飽秀啓; 丸下元治*

JAEA-Research 2022-015, 39 Pages, 2023/05

JAEA-Research-2022-015.pdf:2.74MB

大型放射光施設SPring-8日本原子力研究所専用ビームライン(現在は、日本原子力研究開発機構(JAEA)専用ビームライン)である硬X線アンジュレータビームラインBL22XUの設計を行った。BL22XUは、主に放射性廃棄物処理に係る分離抽出材の設計及び化学的挙動解明を行うためのXAFS(X-ray Absorption Fine Structure)解析実験、回折計を用いた磁性研究実験、高圧プレスやダイヤモンドアンビルセルを用いた極限環境下実験等を行うためのビームラインである。利用可能なX線エネルギー範囲を370keVに設定した。ビームラインの光学系を設計するために、ミラーの反射率、分光結晶の回折幅、Be窓材の吸収率等を計算した。また、光線追跡を行い、各光学素子の材料、寸法、設置場所等を最適化した。さらに、放射性物質利用上の安全確保のため音響遅延管ADL(Acoustic Delay Line)の遅延時間についても検討を行った。BL22XU「重元素科学研究I」は、2002年にビームラインの建設を終え、立ち上げ調整期間を経て、既に運用している。軟X線アンジュレータを光源とするもう一つのJAEA専用ビームラインBL23SU「重元素化科学究II」と共に、2つのビームラインを相補的に利用することによって、原子力科学が直面する多くの問題を解決する放射光ビームラインとして発展することが期待されている。2018年から2019年に分光器の高度化を実施したため、ビームライン建設当時の設計、特徴と性能を改めてここに記録することとした。

論文

Attention-based time series analysis for data-driven anomaly detection in nuclear power plants

Dong, F.*; Chen, S.*; 出町和之*; 吉川雅紀; 関暁之; 高屋茂

Nuclear Engineering and Design, 404, p.112161_1 - 112161_15, 2023/04

https://doi.org/10.1016/j.nucengdes.2023.112161

被引用回数：4 パーセンタイル：96.18(Nuclear Science & Technology)

To ensure nuclear safety, timely and accurate anomaly detection is of utmost importance in the daily condition monitoring of Nuclear Power Plants (NPPs), as any slight anomaly in a plant may result in an irreversible and serious accident, as well as high costs of maintenance and management. Nevertheless, due to the unique inherent attributes of anomalies, the difficulty of automatic detection in NPPs is increased. Previous model-driven anomaly detection approaches required skilled priori knowledge, leading to their limited usability. Commonly adopted deep learning-based data-driven anomaly detection approaches may not easily acquire the most relevant features when dealing with sensor data containing redundant information with uneven distribution of anomalies. To alleviate these issues, this paper propose an attention-based time series model for anomaly detection to ensure safety in NPPs. First, we employ one-dimension convolutional neural network (1D-CNN) backbone for feature extraction to preserve original inherent features of time series inputs. Subsequently, we originally adopt soft-attention mechanism to automatically extract the most relevant temporal features considering the specificity of anomaly detection in NPPs. The performance of the proposed model was experimentally validated on the High Temperature Gas-cooled Reactor (HTGR) anomaly case dataset simulated using the analytical code. The experimental results indicate that the proposed model was capable of detecting anomalies in NPPs with superior performance to the baseline model, while ensuring fast detection at short time steps.

論文

Ferromagnetic crossover within the ferromagnetic order of U $_{7}$ Te $_{12}$

Opletal, P.; 酒井宏典; 芳賀芳範; 常盤欣文; 山本悦嗣; 神戸振作; 徳永陽

Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03

https://doi.org/10.7566/JPSJ.92.034704

被引用回数：1 パーセンタイル：52.21(Physics, Multidisciplinary)

U $_{7}$ Te $_{12}$ の単結晶の物理的性質を調べた。U $_{7}$ Te $_{12}$ が3つの非等価な結晶ウランサイトを持つ六方晶構造を持つことを確認した。常磁性モーメントは、すべてのサイトで一様なモーメントを仮定すると、ウランサイトあたり約1 $mu_{B}$ と推定される。強磁性相転移は $T_{rm C}$ =48Kで発生し、面内磁化は急激に増加するが、面外成分はあまり増加しない。磁場冷却条件下で温度がさらに $T_{rm C}$ 以下に低下すると、面外成分はT $^{star}$ =26K付近で急激に増加する。対照的に、T $^{star}$ 付近で面内成分はほとんど変化しない。比熱測定では、T $^{star}$ 付近に型の異常がないことが示されているため、これらの振る舞いは、秩序した磁気モーメントの再配向、もしくは複数のウランサイトの連続した逐次磁気転移を示唆している。

論文

Characteristic Fermi surface properties in -electron systems

大貫惇睦*; 摂待力生*; 芳賀芳範; 竹内徹也*; 辺土正人*; 仲間隆男*

Quantum Science; The Frontier of Physics and Chemistry, p.21 - 63, 2022/10

https://doi.org/10.1007/978-981-19-4421-5_2

Fermi surfaces of -electron systems and the novel physical properties related with crystal symmetry, electronic correlations and magnetic interactions are reviewed. The key materials are CeRhIn, CeIr, EuCuGe and EuPtSi.

論文

Development of a miniature electromagnet probe for the measurement of local velocity in heavy liquid metals

有吉玄; 大林寛生; 佐々敏信

Journal of Nuclear Science and Technology, 59(9), p.1071 - 1088, 2022/09

https://doi.org/10.1080/00223131.2022.2030824

被引用回数：1 パーセンタイル：27.23(Nuclear Science & Technology)

液体重金属中の局所流速計測において、電磁誘導を用いた計測手法は効果的手法の一つである。永久磁石を利用した流速計として、Ricou and Vives' probeやVon Weissenfluh's probeが広く知られているが、これらの流速計は液温上昇に伴う永久磁石の熱減磁により、流速感度および計測体積が低下することが問題点として挙げられる。特に、永久磁石のキュリー温度を超える温度域では流速検出不能となる。そこで本研究では、流速計が持つ温度依存性の解消を目的とし、小型電磁石を内蔵する流速計を開発した。開発された流速計の直径は6mm、長さは155mmである。流速計の基本性能は、室温環境下における矩形管内水銀流れの局所流速分布計測を通して確認され、流速感度および計測体積が評価された。計測された局所流速分布は数値計算によりその妥当性が確認された。

論文

On the adsorption and reactivity of element 114, flerovium

Yakushev, A.*; Lens, L.*; Dllmann, Ch. E.*; Khuyagbaatar, J.*; Jger, E.*; Krier, J.*; Runke, J.*; Albers, H. M.*; 浅井雅人; Block, M.*; et al.

Frontiers in Chemistry (Internet), 10, p.976635_1 - 976635_11, 2022/08

https://doi.org/10.3389/fchem.2022.976635

被引用回数：11 パーセンタイル：81.01(Chemistry, Multidisciplinary)

114番元素フレロビウム(Fl)は現在その化学的性質が研究されている最も重い元素である。Flに関する最初の化学実験では、Flは貴ガス的な性質を持つ元素であると報告された。一方、2番目の研究では、Flは揮発性金属の性質を示すと報告された。より信頼性の高い結論を得るため、我々は更なる実験的研究を行い、二酸化ケイ素と金表面におけるFlの吸着挙動を調べた。その結果、Flは揮発性金属の水銀よりも高い揮発性と低い反応性を示し、一方、貴ガスのラドンよりは反応性が高いことを明らかにした。

論文

Single crystal growth and magnetic properties of noncentrosymmetric antiferromagnet MnIrSi

大貫惇睦*; 金子良夫*; 青木大*; 仲村愛*; 松田達磨*; 中島美帆*; 芳賀芳範; 竹内徹也*

Journal of the Physical Society of Japan, 91(6), p.065002_1 - 065002_2, 2022/06

https://doi.org/10.7566/JPSJ.91.065002

被引用回数：2 パーセンタイル：42.15(Physics, Multidisciplinary)

Single crystals of MnIrSi were grown using Bridgman method. MnIrSi shows a remarkable increase of the electrical resistivity below antiferromagnetic transition temperature accompanied by a large jump of specific heat.

論文

Abrupt change in electronic states under pressure in new compound EuPtAl

小泉尭嗣*; 本多史憲*; 佐藤芳樹*; Li, D.*; 青木大*; 芳賀芳範; 郷地順*; 長崎尚子*; 上床美也*; 金子良夫*; et al.

Journal of the Physical Society of Japan, 91(4), p.043704_1 - 043704_5, 2022/04

https://doi.org/10.7566/JPSJ.91.043704

被引用回数：2 パーセンタイル：42.15(Physics, Multidisciplinary)

A new ternary europium compound EuPtAl is reported. It orders antiferromagnetically at 12.4 K. Application of hydrostatic pressure varies the transition temperature and the compound becomes non-magnetic above the critical pressure 9 GPa. The pressure-temperature phase diagram is indicative of a possible valence crossover at the critical pressure.

論文

Half-integer Shapiro steps in strong ferromagnetic Josephson junctions

Yao, Y.*; Cai, R.*; Yang, S.-H.*; Xing, W.*; Ma, Y.*; 森道康; Ji, Y.*; 前川禎通; Xie, X.-C.*; Han, W.*

Physical Review B, 104(10), p.104414_1 - 104414_6, 2021/09

https://doi.org/10.1103/PhysRevB.104.104414

被引用回数：3 パーセンタイル：25.71(Materials Science, Multidisciplinary)

We report the experimental observation of half-integer Shapiro steps in the strong ferromagnetic Josephson junction (Nb-NiFe-Nb) by investigating the current-phase relation under radio-frequency microwave excitation. The half-integer Shapiro steps are robust in a wide temperature range from T = 4 to 7 K. The half-integer Shapiro steps could be attributed to co-existence of 0- and -states in the strong ferromagnetic NiFe Josephson junctions with the spatial variation of the NiFe thickness. This scenario is also supported by the high-resolution transmission electron microscopy characterization of the Nb/NiFe/Nb junction.

論文

Probing the long-range structure of the $T^{+}_{cc}$ with the strong and electromagnetic decays

Meng, L.*; Wang, G.-J.*; Wang, B.*; Zhu, S.-L.*

Physical Review D, 104(5), p.L051502_1 - L051502_8, 2021/09

https://doi.org/10.1103/PhysRevD.104.L051502

被引用回数：56 パーセンタイル：98.46(Astronomy & Astrophysics)

最近発見された $T^+_{cc}$ 状態の長距離構造をその強い相互作用と電磁相互作用による崩壊の分岐の様子から推定することが可能であることを示した。その結果、 $T_{cc}$ の主成分は $D^{*+}D^0$ であることがわかった。

論文

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe

野間雄一郎*; 小手川恒*; 久保徹郎*; 藤秀樹*; 播磨尚朝*; 芳賀芳範; 山本悦嗣; 大貫惇睦*; 伊藤公平*; 仲村愛*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

https://doi.org/10.7566/JPSJ.90.073707

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

Ferromagnetic fluctuation relevant to the pressure-induced superconductivity in UGe is investigated by means of NMR spectroscopy. Longitudinal magnetic fluctuations were observed in the spin-echo decay rate near the ferromagnetic critical point where superconductivity takes place. This result strongly suggests that superconductivity in ferromagnets is universally mediated by anisotropic magnetic fluctuations.

論文

Anisotropic physical properties of layered antiferromagnet UPtGa $_{15}$

松本裕司*; 芳賀芳範; 山本悦嗣; 竹内徹也*; 三宅厚志*; 徳永将史*

Journal of the Physical Society of Japan, 90(7), p.074707_1 - 074707_6, 2021/07

https://doi.org/10.7566/JPSJ.90.074707

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

A uranium intermetallic compound UPtGa $_{15}$ was successfully synthesized. This compound crystallizes in the hexagonal Sc $_{0.6}$ FeSi $_{4.9}$ -type structure. Antiferromagnetic transition with highly magnetic anisotropy was established by the physical property measurements.

論文

Nonmagnetic-magnetic transition and magnetically ordered structure in SmS

吉田章吾*; 小山岳秀*; 山田陽彦*; 中井祐介*; 上田光一*; 水戸毅*; 北川健太郎*; 芳賀芳範

Physical Review B, 103(15), p.155153_1 - 155153_5, 2021/04

https://doi.org/10.1103/PhysRevB.103.155153

被引用回数：1 パーセンタイル：7.22(Materials Science, Multidisciplinary)

SmS, a protopypical intermediate valence compound, has been studied by performing high-pressure nuclear magnetic resonance measurements. The observation of an additional signal at high pressure gives evidence of a magnetic phase transition. The cancellation of the hyperfined fields at the S site suggests a type-II antiferromagnetic structure.

論文

Feasibility study of magnetic-domain observation by means of non-resonant magnetic X-ray diffraction

稲見俊哉*; 菖蒲敬久; 石井賢司*

IEEE Transactions on Magnetics, 57(3, Part 2), p.6400105_1 - 6400105_5, 2021/03

https://doi.org/10.1109/TMAG.2020.3046006

被引用回数：0 パーセンタイル：0.00(Engineering, Electrical & Electronic)

Although the observation of magnetic domains well below the surface of a sample appears to be relatively easy, in reality, magnetic domains inside metallic samples have not been investigated in detail due to a lack of adequate techniques. Non-resonant magnetic X-ray diffraction (NRMXRD) is a candidate for such 3-D magnetic microscopy. A relatively small focus size of less than 100 nm and a relatively long attenuation length of more than 100 m can be obtained by using high-energy synchrotron X-rays. However, NRMXRD has a disadvantage in that the magnetic contrast is low. It is known that the magnetic contrast in NRMXRD increases with increasing the total polarization of the incident X-rays. In this feasibility study, we carried out NRMXRD experiments on a metallic iron sample to examine whether the magnetic contrast can be sufficiently enhanced even for high-energy X-rays.

論文

Intriguing behavior of UCo $_{1-x}$ RhGe ferromagnets in magnetic field along the axis

Pospil, J.*; 芳賀芳範; 三宅厚志*; 神戸振作; 徳永陽; 徳永将史*; 山本悦嗣; Proschek, P.*; Voln, J.*; Sechovsk, V.*

Physical Review B, 102(2), p.024442_1 - 024442_13, 2020/07

https://doi.org/10.1103/PhysRevB.102.024442

被引用回数：6 パーセンタイル：37.51(Materials Science, Multidisciplinary)

Alloying study of ferromagnetic superconductors URhGe and UCoGe is reported. The Curie temperature shows a maximum at Rh concentration = 0.4 in UCo $_{1-x}$ RhGe. Magnetic characteristices in low- and high- regions are significantly different each other. The relationship between magnetism and superconductivity are discussed.