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Cu(PO
)SO 
5HO as a model antiferromagnetic spin-1/2 Heisenberg 
- chain藤原 理賀; Jeschke, H. O.*; 森田 克洋*; 桑井 智彦*; 幸田 章宏*; 岡部 博孝*; 松尾 晶*; 金道 浩一*; 満田 節生*
Physical Review Materials (Internet), 6(11), p.114408_1 - 114408_8, 2022/11
被引用回数：0 パーセンタイル：0(Materials Science, Multidisciplinary)
= 1/2ハイゼンベルグ-反強磁性鎖は、エキゾチックなスピン状態の発現が予想されており、広く研究されている。この論文では、birchiteと呼ばれる銅鉱物、化学式CdCu(PO)SO5HOの磁気挙動とその有効スピンモデルについて報告する。帯磁率,磁化,比熱,
SR測定による実験的研究から、0.4Kまで長距離秩序を示さないことがわかった。理論研究から、birchiteは-反強磁性鎖のモデル化合物であり、鎖内相互作用、は反強磁性的で、その大きさは鎖間相互作用の約100倍であることがわかった。の大きさはの大きさの2
3倍であるため、スピンギャップはの数%に過ぎないと予想される。比熱の温度依存性は約1Kでブロードなピーク(
0.036)を示し、スピンギャップの存在が示唆された。
西村 昇一郎*; 鳥居 寛之*; 深尾 祥紀*; 伊藤 孝; 岩崎 雅彦*; 神田 聡太郎*; 川越 清以*; Kawall, D.*; 河村 成肇*; 黒澤 宣之*; et al.
Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08
被引用回数：8 パーセンタイル：79.69(Optics)As a method to determine the resonance frequency, Rabi-oscillation spectroscopy has been developed. In contrast to conventional spectroscopy which draws the resonance curve, Rabi-oscillation spectroscopy fits the time evolution of the Rabi oscillation. By selecting the optimized frequency, it is shown that the precision is twice as good as conventional spectroscopy with a frequency sweep. Furthermore, the data under different conditions can be treated in a unified manner, allowing more efficient measurements for systems consisting of a limited number of short-lived particles produced by accelerators such as muons. We have developed a fitting function that takes into account the spatial distribution of muonium and the spatial distribution of the microwave intensity to apply this method to ground-state muonium hyperfine structure measurements at zero field. It was applied to the actual measurement data, and the resonance frequencies were determined under various conditions. The result of our analysis gives 
= 4 463 301.61 
0.71 kHz.
藤原 理賀*; 森田 克洋*; Mole, R.*; 満田 節生*; 遠山 貴巳*; 矢野 真一郎*; Yu, D.*; 曽田 繁利*; 桑井 智彦*; 幸田 章宏*; et al.
Nature Communications (Internet), 11, p.3429_1 - 3429_7, 2020/07
被引用回数：21 パーセンタイル：86.79(Multidisciplinary Sciences)Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two-dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu
AlBiO
(SO)
Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation, and inelastic neutron scattering measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.
中根 僚宏*; 米山 翔太*; 兒玉 健*; 菊地 耕一*; 中尾 朗子*; 大原 高志; 東中 隆二*; 松田 達磨*; 青木 勇二*; 藤田 渉*
Dalton Transactions (Internet), 48(1), p.333 - 338, 2019/01
被引用回数：2 パーセンタイル：13.9(Chemistry, Inorganic & Nuclear)The two-dimensional quadratic lattice magnet, bis(glycolato)cobalt(II) ([Co(HOCHCO)]), showed anti-ferromagnetic ordering at 15.0 K and an abrupt increase in magnetisation at H = 22 600 Oe and 2 K, thereby acting as a metamagnet. Neutron diffraction studies suggested that the magnetic moment vectors of the Co(II) ions had an amplitude of 3.59 mB and were not aligned in a fully antiparallel fashion to those of their neighbours, which caused canting between the magnetic moment vectors in the sheet. The canting angle was determined to be 7.1deg. Canting induced net magnetisation in the sheet, but this magnetisation was cancelled between sheets. The magnetisations in the sheets were oriented parallel to the magnetic field at the critical magnetic field.
Strasser, P.*; 阿部 充志*; 青木 正治*; Choi, S.*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; et al.
EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01
被引用回数：13 パーセンタイル：99.33High precision measurements of the ground state hyperfine structure (HFS) of muonium is a stringent tool for testing bound-state quantum electrodynamics (QED) theory, determining fundamental constants of the muon magnetic moment and mass, and searches for new physics. Muonium is the most suitable system to test QED because both theoretical and experimental values can be precisely determined. Previous measurements were performed decades ago at LAMPF with uncertainties mostly dominated by statistical errors. At the J-PARC Muon Science Facility (MUSE), the MuSEUM collaboration is planning complementary measurements of muonium HFS both at zero and high magnetic field. The new high-intensity muon beam that will soon be available at H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation for high-field measurements, and the latest results at zero field are presented.
坂本 浩幸*; 赤木 洋介*; 山田 一夫*; 舘 幸男; 福田 大祐*; 石松 宏一*; 松田 樹也*; 齋藤 希*; 上村 実也*; 浪平 隆男*; et al.
日本原子力学会和文論文誌, 17(2), p.57 - 66, 2018/05
福島第一原子力発電所の事故によって放射性セシウムによって汚染されたコンクリート瓦礫が発生しており、さらに、将来の原子炉の廃止措置に伴って多量の放射性コンクリート廃棄物が生じることが想定される。床や壁等のフラットな表面の除染には既存技術が有効であるが、コンクリート瓦礫に対する除染技術の適用性については課題がある。本研究では、パルスパワー放電技術の適用性可能性に着目して、汚染コンクリートの骨材とセメントペーストへの分離と、それぞれの放射能測定による基礎的な試験と評価を実施した。試験結果より、汚染コンクリートの骨材とセメントペーストへの分離によって、放射性コンクリートの除染と減容が達成される可能性が示された。
上野 恭裕*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; 伊藤 孝; 岩崎 雅彦*; et al.
Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11
被引用回数：3 パーセンタイル：87.03MuSEUM is an international collaboration aiming at a new precise measurement of the muonium hyperfine structure at J-PARC (Japan Proton Accelerator Research Complex). Utilizing its intense pulsed muon beam, we expect a ten-fold improvement for both measurements at high magnetic field and zero magnetic field. We have developed a sophisticated monitoring system, including a beam profile monitor to measure the 3D distribution of muonium atoms to suppress the systematic uncertainty.
=1/2 quasi-one-dimensional Ising-like antiferromagnet BaCoVO
in a transverse magnetic field松田 雅昌*; 大西 弘明; 奥谷 顕*; Ma, J.*; Agrawal, H.*; Hong, T.*; Pajerowski, D. M.*; Copley, J. R. D.*; 奥西 巧一*; 森 道康; et al.
Physical Review B, 96(2), p.024439_1 - 024439_8, 2017/07
被引用回数：11 パーセンタイル：52.02(Materials Science, Multidisciplinary)BaCoVO consists of Co chains, in which Co
ion carries a fictitious spin 
with Ising anisotropy. We performed elastic and inelastic neutron scattering experiments in BaCoVO in magnetic field perpendicular to the 
axis which is the chain direction. With applying magnetic field along the 
axis at 3.5 K, the antiferromagnetic order with the easy axis along the axis, observed in zero magnetic field, is completely suppressed at 8 T, while the magnetic field gradually induces an antiferromagnetic order with the spin component along the 
axis. We also studied magnetic excitations as a function of transverse magnetic field. The lower boundary of the spinon excitations splits gradually with increasing magnetic field. The overall feature of the magnetic excitation spectra in magnetic field is reproduced by the theoretical calculation based on the spin 
antiferromagnetic chain model, which predicts that the dynamic magnetic structure factor of the spin component along the chain direction is enhanced and that along the field direction has clear incommensurate correlations.
Strasser, P.*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; 伊藤 孝; 岩崎 雅彦*; et al.
Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12
被引用回数：7 パーセンタイル：92.26At the Muon Science Facility (MUSE) of J-PARC (Japan Proton Accelerator Research Complex), the MuSEUM collaboration is planning new measurements of the ground state hyperfine structure (HFS) of muonium both at zero field and at high magnetic field. The previous measurements were performed both at LAMPF (Los Alamos Meson Physics Facility) with experimental uncertainties mostly dominated by statistical errors. The new high intensity muon beam that will soon be available at MUSE H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation, and the results of a first commissioning test experiment at zero field are presented.
大島 武; 横関 貴史; 村田 航一; 松田 拓磨; 三友 啓; 阿部 浩之; 牧野 高紘; 小野田 忍; 土方 泰斗*; 田中 雄季*; et al.
Japanese Journal of Applied Physics, 55(1S), p.01AD01_1 - 01AD01_4, 2016/01
被引用回数：11 パーセンタイル：49.67(Physics, Applied)In this study, we report the effects of 
-ray irradiation and subsequent annealing on the electrical characteristics of vertical structure power 4H Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) with the blocking voltage of 1200 V. The MOSFETs were irradiated with -rays up to 1.2 MGy in a N atmosphere at room temperature (RT). During the irradiation, no bias was applied to each electrode of the MOSFETs. After the irradiation, the MOSFETs were kept at RT for 240 h to investigate the stability of their degraded characteristics. Then, the irradiated MOSFETs were annealed up to 360 
C in the atmosphere. The current-voltage (I-V) characteristics of the MOSFETs were measured at RT. By 1.2 MGy irradiation, the shift of threshold voltage (V
) for the MOSFETs was -3.39 V. After RT preservation for 240 h, MOSFETs showed no significant recovery in V. By annealing up to 360 C, the MOSFETs showed remarkable recovery, and the values of V become 91 % of the initial values. Those results indicate that the degraded characteristics of SiC MOSFETs can be recovered by thermal annealing at 360 C.
-YbAlB at high magnetic fields寺島 拓*; 松田 康弘*; 久我 健太郎*; 鈴木 慎太郎*; 松本 洋介*; 中辻 知*; 近藤 晃弘*; 金道 浩一*; 河村 直己*; 水牧 仁一朗*; et al.
Journal of the Physical Society of Japan, 84(11), p.114715_1 - 114715_4, 2015/11
被引用回数：4 パーセンタイル：36.22(Physics, Multidisciplinary)-YbAlB shows strong valence fluctuation as well as heavy fermion behavior at low temperatures. It has been theoretically suggested that the quantum criticality owing to the valence fluctuation found in Yb ions plays an important role in the peculiar properties of this material. In this work, we measured the X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) at the L3 edge of Yb ions in high magnetic fields of up to 40 T. It is found that the XAS are almost independent of the magnetic field at 2 K, which proves that there is no significant valence change in this field range. The XMCD spectrum exhibits a distinct negative peak at the low-energy side of the L3 edge as well as the main positive peak near the white line. The negative XMCD peak is attributed to the quadrupole transition between the 2p and 4f states, and gives us microscopic information on the 4f state. This finding supports the recent theoretical proposal that 
is the ground state of the localized Yb magnetic moment, where 
is the z-component of the total angular momentum of Yb
.
土方 泰斗*; 三友 啓*; 松田 拓磨*; 村田 航一*; 横関 貴史*; 牧野 高紘; 武山 昭憲; 小野田 忍; 大久保 秀一*; 田中 雄季*; et al.
Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.130 - 133, 2015/11
In order to develop semiconductor devices with MGy radiation resistivity, we are developing power metal-oxide-semiconductor field-effect-transistors (MOSFETs) based on silicon carbide (SiC) semiconductors. The -ray irradiation responses of power SiC-MOSFETs were studied under various irradiation temperatures and humidity with various gate-bias conditions. Making comparisons between these responses, the optimum device operating condition and a better device structure were derived and MGy resistivity was achieved. Besides, -ray irradiation tests for a motor-driver circuits consisting of SiC-MOSFETs were carried out, and as a result, their continuous operation up to 2 MGy was confirmed.
武山 昭憲; 松田 拓磨; 横関 貴史; 三友 啓; 村田 航一; 牧野 高紘; 小野田 忍; 田中 雄季*; 神取 幹郎*; 吉江 徹*; et al.
Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.134 - 137, 2015/11
Influence of -ray irradiation under high temperature and high humidity circumstance on the electrical characteristics of Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) was investigated. The drain current (I
)-gate voltage (V
) curves shifted to the negative voltage side and no significant further shift was observed with increasing the dose above 10 kGy. Suppression of the negative shift of threshold voltage (V
) means that positive charges generated by irradiation were thermally annealed by elevated temperature during irradiation. The leakage current slightly increased at 5 and 10 kGy, however, those values recovered to be approximately the initial value above 40 kGy. Humidity circumstance attributed to remarkable suppression of the leakage current in comparison with dry circumstance.
津田 修一; 吉田 忠義; 安藤 真樹; 松田 規宏; 三上 智; 谷垣 実*; 奥村 良*; 高宮 幸一*; 佐藤 信浩*; 関 暁之; et al.
Radioisotopes, 64(4), p.275 - 289, 2015/04
環境中における空間線量率測定に関する実用面で役に立つ情報を提供する。この中で、精度の高い測定に必要とされる基本的要件について実データを例示しながら説明するとともに、信頼のおける環境測定に広く使用されている手法の特徴や測定例について紹介する。また、これまでに公的機関を中心に測定された空間線量率やこれに関連したデータを閲覧できるインターネットサイトに関する情報を提供する。
-YbAl
Fe
B (
) at low temperatures and high magnetic fields寺島 拓*; 松田 康弘*; 久我 健太郎*; 鈴木 慎太郎*; 松本 洋介*; 中辻 知*; 近藤 晃弘*; 金道 浩一*; 河村 直己*; 水牧 仁一朗*; et al.
Journal of Physics; Conference Series, 592(1), p.012020_1 - 012020_6, 2015/03
被引用回数：1 パーセンタイル：44.15価数転移に伴う量子臨界現象が理論的に提案され、希土類金属間化合物における価数揺動現象が注目を集めている。最近、
-YbAlBがチューニングなしで量子臨界を示すことと強い混合原子価状態にあることが見出された。この研究では我々は-YbAlFeB ()について磁化曲線とX線吸収を測定した。この物質は、局所的には-YbAlBと同一構造をもつ多形である。磁化測定とX線測定はそれぞれ55Tと40Tまで行った。Yb価数のわずかな上昇が磁化曲線が傾きの変化を示す磁場で観測された。
安藤 真樹; 中原 由紀夫; 津田 修一; 吉田 忠義; 松田 規宏; 高橋 史明; 三上 智; 木内 伸幸; 佐藤 哲朗*; 谷垣 実*; et al.
Journal of Environmental Radioactivity, 139, p.266 - 280, 2015/01
被引用回数：49 パーセンタイル：84.06(Environmental Sciences)福島第一原子力発電所周辺の空間線量率分布を評価し空間線量率の経時変化傾向を把握するため、KURAMA及びKURAMA-IIシステムを用いた一連の走行サーベイを2011年6月から2012年12月まで東日本の広範囲において実施した。約100台の装置を用いて得られる大量のデータを短時間に解析する自動処理システムを開発した。第1次走行サーベイにおいて放射性セシウムの移行状況を調査するための初期データを取得し、その後の走行サーベイにおいて測定範囲を拡大して測定を実施した。空間線量率の経時変化について調べた結果、放射性セシウムの物理減衰による減少やNaI(Tl)サーベイメータを用いた道路周辺の攪乱のない平坦地での測定結果よりも走行サーベイでの測定結果の方が減少の割合が大きいことが分かった。
伊藤 孝; 豊田 晃久*; 髭本 亘; 田島 美典*; 松田 恭幸*; 下村 浩一郎*
Nuclear Instruments and Methods in Physics Research A, 754, p.1 - 9, 2014/08
被引用回数：7 パーセンタイル：50.6(Instruments & Instrumentation)A new muon beam profile monitor (MBPM) was developed to diagnose pulsed muon beams in J-PARC MUSE, mainly composed of a scintillation screen, a gated image intensifier (II), and a cooled CCD camera. The MBPM was designed to be compact so that it could be inserted into the bore of the SR spectrometer in the D1 area and used concurrently. The spatial resolution of the MBPM was evaluated to be in the range from one to two line-pair/mm, depending on II gain. Such high-resolution muon beam profiles were obtained online for a positive muon beam with a kinetic energy of 4 MeV. The contribution from decay positrons was significantly reduced owing to II gating. The linearity of the MBPM was evaluated on the bases of the number of decay positrons monitored by the SR spectrometer. A linear response within five percent deviations was confirmed over more than two orders of magnitude. In addition, 3D imaging capability, use in vacuum, and immunity against moderate magnetic fields were demonstrated.
Si observed by X-ray absorption spectroscopy中井 裕人*; 海老原 孝雄*; 筒井 智嗣*; 水牧 仁一朗*; 河村 直己*; 道村 真司*; 稲見 俊哉; 中村 俊幸*; 近藤 晃弘*; 金道 浩一*; et al.
Journal of the Physical Society of Japan, 82(12), p.124712_1 - 124712_5, 2013/12
被引用回数：7 パーセンタイル：48.56(Physics, Multidisciplinary)重い電子化合物であるYbRhSiのYb価数の温度磁場依存性をX線吸収分光で観測した。測定からは、何れも突然の変化なしに、Yb価数が2Kから200Kの範囲で温度の下降に伴い減少することと、0Tから33Tの範囲で磁場の増加に伴い増加することが明かになった。Ybの価数は、磁場と温度に依存して、2.92から2.96の範囲であった。価数が2Kでは0Tで2.92で33Tで2.93である点で、YbRhSiは価数揺動状態にあることがわかり、高磁場でも整数価数に届かない。これらの結果はYbの価数が整数価数の3+に非常に近く、降温に伴い減少し、磁場の印加に伴い3+に近づくというこれまでの知識を支持するものである。
津田 修一; 吉田 忠義; 中原 由紀夫; 佐藤 哲朗; 関 暁之; 松田 規宏; 安藤 真樹; 武宮 博; 谷垣 実*; 高宮 幸一*; et al.
JAEA-Technology 2013-037, 54 Pages, 2013/10
JAEA-Technology-2013-037.pdf:4.94MB
東京電力福島第一原子力発電所事故後における広域の詳細な空間線量率マップを作成するために、原子力機構は走行サーベイシステムKURAMA-IIを用いた測定を文部科学省の委託を受けて実施した。KURAMAは、一般乗用車に多数搭載して広範囲の空間線量率を詳細かつ短期間に把握することを目的として京都大学原子炉実験所で開発されたシステムである。KURAMAは、エネルギー補償型線検出器で測定した線量率をGPSの測位データでタグ付けしながら記録する測定器、データを受け取り可視化のための処理や解析を行うサーバ、エンドユーザがデータを閲覧するためのクライアントから構成される。第2世代のKURAMA-IIでは更なる小型化、堅牢性の向上、データ送信の完全自動化等の機能が強化されたことによって、100台の同時測定が可能となり、広域の詳細な線量率マッピングをより短期間で実施することが可能になった。本報告では、KURAMA-IIによる測定データの信頼性を確保するために実施した基盤整備と、KURAMA-IIを空間線量率マッピング事業に適用した結果について述べるとともに、多数のKURAMA-IIを使用した走行サーベイの精度を保証するための効率的なKURAMA-IIの管理方法を提案した。
伊藤 孝; 髭本 亘; 松田 達磨*; 幸田 章宏*; 下村 浩一郎*
Applied Physics Letters, 103(4), p.042905_1 - 042905_4, 2013/07
被引用回数：10 パーセンタイル：42.64(Physics, Applied)The influence of hydrogen impurities on electronic properties of undoped BaTiO was studied from a microscopic point of view using the muon spin rotation and relaxation technique. Electron localization around an implanted positive muon, by analogy an hydrogen impurity, was observed below 80 K. The effective electron binding energy was estimated to be 
eV, indicating that the hydrogen-induced defect forms a shallow donor level. At room temperature, the weakly bound electron is excited into a conduction band and behaves as a free carrier, which causes insulation degradation undesirable for capacitor application.
