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論文

Local electronic structure of interstitial hydrogen in MgH inferred from muon study

門野良典*; 平石雅俊*; 岡部博孝*; 幸田章宏*; 伊藤孝

Journal of Physics; Condensed Matter, 35(28), p.285503_1 - 285503_13, 2023/07

https://doi.org/10.1088/1361-648X/acccc7

Magnesium hydride has great potential as a solid hydrogen (H) storage material because of its high H storage capacity of 7.6 wt%. However, its slow hydrogenation and dehydrogenation kinetics and the high temperature of 300 C required for decomposition are major obstacles to small-scale applications such as automobiles. The local electronic structure of interstitial H in MgH is an important fundamental knowledge in solving this problem, which has been studied mainly based on density functional theory (DFT). However, few experimental studies have been performed to assess the results of DFT calculations. We have therefore introduced muon (Mu) as pseudo-H into MgH and investigated the corresponding interstitial H states by analyzing their electronic and dynamical properties in detail. As a result, we observed multiple Mu states similar to those observed in wide-gap oxides, and found that their electronic states can be attributed to relaxed-excited states associated with donor/acceptor levels predicted by the recently proposed ambipolarity model. This provides an indirect support for the DFT calculations on which the model is based via the donor/acceptor levels. An important implication of the muon results for improved hydrogen kinetics is that dehydrogenation, serving as a reduction for hydrides, stabilises the interstitial H state.

論文

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters

大熊隆太郎*; 古府麻衣子; 浅井晋一郎*; Avdeev, M.*; 幸田章宏*; 岡部博孝*; 平石雅俊*; 竹下聡史*; 小嶋健児*; 門野良典*; et al.

Nature Communications (Internet), 12, p.4382_1 - 4382_7, 2021/07

https://doi.org/10.1038/s41467-021-24636-1

被引用回数：5 パーセンタイル：63.64(Multidisciplinary Sciences)

Dimensionality is a critical factor in determining the properties of solids and is an apparent built- in character of the crystal structure. However, it can be an emergent and tunable property in geometrically frustrated spin systems. Here, we study the spin dynamics of the tetrahedral cluster antiferromagnet, pharmacosiderite, via muon spin resonance and neutron scattering. We find that the spin correlation exhibits a two-dimensional characteristic despite the isotropic connectivity of tetrahedral clusters made of spin 5/2 Fe $^{3+}$ ions in the three-dimensional cubic crystal, which we ascribe to two-dimensionalisation by geometrical frustration based on spin wave calculations. Moreover, we suggest that even one-dimensionalisation occurs in the decoupled layers, generating low-energy and one-dimensional excitation modes, causing large spin fluctuation in the classical spin system.

論文

Origin of magnetovolume effect in a cobaltite

Miao, P.*; Tan, Z.*; Lee, S. H.*; 石川喜久*; 鳥居周輝*; 米村雅雄*; 幸田章宏*; 小松一生*; 町田真一*; 佐野亜沙美; et al.

Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03

https://doi.org/10.1103/PhysRevB.103.094302

被引用回数：1 パーセンタイル：0(Materials Science, Multidisciplinary)

層状ペロブスカイトPrBaCo $_{2}$ O $_{5.5}$ は、熱膨張のない複合材料を作るために必要な負の熱膨張(NTE)を示す。NTEは、自発的な磁気秩序と密接に関連していることがわかっていた(磁気体積効果: MVE)。今回、われわれは、PrBaCo $_{2}$ O $_{5.5}$ の連続的な磁気体積効果が、本質的には不連続であり、大きな体積を持つ反強磁性絶縁体(AFILV)から、小さな体積をもつ強磁性卑絶縁体(FLISV)への磁気電気的相転移に起因することを明らかにした。また、磁気電気効果(ME)は、温度,キャリアドーピング,静水圧,磁場などの複数の外部刺激に対して高い感度を示した。これは、これまでよく知られている対称性の破れを伴う巨大磁気抵抗やマルチフェロイック効果などのMEとは対照的であり、輝コバルト鉱のMEは同一の結晶構造で起こる。われわれの発見は、MEとNTEを実現するための新しい方法を示しており、それは新しい技術に応用されるかもしれない。

論文

Quantum dynamics of hydrogen in the iron-based superconductor LaFeAsO $_{0.9}$ D $_{0.1}$ measured with inelastic neutron spectroscopy

山浦淳一*; 平賀晴弘*; 飯村壮史*; 村場善行*; Bang, J.*; 池内和彦*; 中村充孝; 稲村泰弘; 本田孝志*; 平石雅俊*; et al.

Physical Review B, 99(22), p.220505_1 - 220505_6, 2019/06

AA2019-0126.pdf:0.9MB

https://doi.org/10.1103/PhysRevB.99.220505

被引用回数：1 パーセンタイル：5.4(Materials Science, Multidisciplinary)

鉄系超伝導体LaFeAsO $_{0.9}$ D $_{0.1}$ の非弾性中性子散乱実験により、超伝導転移温度26K以下において、5-15meVのエネルギー領域に新しい励起が生じることを見出した。なお、この励起は母物質であるLaFeAsO $_{0.9}$ F $_{0.1}$ では現れない。14.5meVと11.1meVに現れる強い励起は水素の量子ラットリングまたはバンド運動に起因し、格子間サイトが2個以上のポテンシャル極小点を有する場合にのみ出現するものと結論付けた。

論文

Quantum magnetisms in uniform triangular lattices Li $_{2}$ Mo $_{3}$ O $_{8}$ ( = In, Sc)

飯田一樹*; 吉田紘行*; 岡部博孝*; 片山尚幸*; 石井裕人*; 幸田章宏*; 稲村泰弘; 村井直樹; 石角元志*; 門野良典*; et al.

Scientific Reports (Internet), 9(1), p.1826_1 - 1826_9, 2019/02

https://doi.org/10.1038/s41598-018-36123-7

被引用回数：8 パーセンタイル：59.47(Multidisciplinary Sciences)

Molecular based spin-1/2 triangular lattice systems have attracted research interest. LiMoO ( = In or Sc) is such a compound where spin-1/2 MoO $_{13}$ clusters in place of Mo ions form the uniform triangular lattice. Here, we report exotic magnetisms in LiInMoO and LiScMoO investigated by muon spin rotation (SR) and inelastic neutron scattering (INS) spectroscopies. LiInMoO exhibits spin wave excitation which is quantitatively described by the nearest neighbor anisotropic Heisenberg model based on the 120 $^{circ}$ spin structure. In contrast, LiScMoO undergoes short-range magnetic order below 4 K with quantum-spin-liquid-like magnetic fluctuations down to the base temperature. Origin of the different ground states is discussed in terms of anisotropies of crystal structures and magnetic interactions.

論文

New precise measurements of muonium hyperfine structure at J-PARC MUSE

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

https://doi.org/10.1051/epjconf/201919800003

被引用回数：13 パーセンタイル：99.42

High 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.

論文

New precise measurement of muonium hyperfine structure interval at J-PARC

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

https://doi.org/10.1007/s10751-016-1381-7

被引用回数：3 パーセンタイル：86.81

MuSEUM 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.

論文

Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex, 4; The Muon Facility

髭本亘; 門野良典*; 河村成肇*; 幸田章宏*; 小嶋健児*; 牧村俊助*; 的場史郎*; 三宅康博*; 下村浩一郎*; Strasser, P.*

Quantum Beam Science (Internet), 1(1), p.11_1 - 11_24, 2017/06

https://doi.org/10.3390/qubs1010011

ミュオン科学実験施設はJ-PARCにおいて中性子, ハドロン, ニュートリノ各施設と並ぶ利用施設である。ミュオン施設では、物質生命科学実験棟において中性子実験施設と共有している高エネルギーの陽子により発生させたミュオンを用いて様々な科学研究に用いている。本レビューではミュオン科学実験施設の現状について報告する。

論文

New muonium HFS measurements at J-PARC/MUSE

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

https://doi.org/10.1007/s10751-016-1331-4

被引用回数：7 パーセンタイル：92.03

At 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.

論文

Tuning of ultra-slow muon transport system

足立泰平*; 池戸豊*; 西山樟生*; 薮内敦*; 長友傑*; Strasser, P.*; 伊藤孝; 髭本亘; 小嶋健児*; 牧村俊助*; et al.

JPS Conference Proceedings (Internet), 8, p.036017_1 - 036017_4, 2015/09

https://doi.org/10.7566/JPSCP.8.036017

We report on the tuning of the ultra-slow muon beam line at J-PARC MUSE using Li impurities in a tungsten muonium production target in place of positive muons. Li ions were evaporated from the tungsten target by heating it up to 2000K and were transported in the ultra-slow muon beam line. The Li ion beam was monitored by micro channel plates installed at several points in the beam line. The Li beam was successfully transported to the end of the beam line after optimization of beam line parameters.

論文

Bipartite magnetic parent phases in the iron oxypnictide superconductor

平石雅俊*; 飯村壮史*; 小嶋健児*; 山浦淳一*; 平賀晴弘*; 池田一貴*; Miao, P.*; 石川喜久*; 鳥居周輝*; 宮崎正範*; et al.

Nature Physics, 10(4), p.300 - 303, 2014/04

https://doi.org/10.1038/nphys2906

被引用回数：101 パーセンタイル：95.69(Physics, Multidisciplinary)

High-temperature (high- $T_{rm c}$ ) superconductivity appears as a consequence of the carrier-doping of an undoped parent compound exhibiting antiferromagnetic order; thereby, ground-state properties of the parent compound are closely relevant to the superconducting state. On the basis of the concept, a spin-fluctuation has been addressed as an origin of pairing of the superconducting electrons in cuprates. Whereas, there is growing interest in the pairing mechanism such as an unconventional spin-fluctuation or an advanced orbital-fluctuation due to the characteristic multi-orbital system in iron-pnictides. Here, we report the discovery of an antiferromagnetic order as well as a unique structural transition in electron-overdoped LaFeAsO $_{1-x}$ H (), whereby another parent phase was uncovered, albeit heavily doped. The unprecedented two-dome superconducting phases observed in this material can be interpreted as a consequence of the carrier-doping starting from the original at and advanced at parent phases toward the intermediate region. The bipartite parent phases with distinct physical properties in the second magnetic phase provide us with an interesting example to illustrate the intimate interplay among the magnetic interaction, structural change and orbital degree of freedom in iron-pnictides.

論文

Suppression of time-reversal symmetry breaking superconductivity in Pr(Os $_{1-x}$ Ru)Sb $_{12}$ and Pr $_{1-y}$ LaOsSb $_{12}$

Shu, L.*; 髭本亘; 青木勇二*; Hillier, A. D.*; 大石一城*; 石田憲二*; 門野良典*; 幸田章宏*; Bernal, O. O.*; MacLaughlin, D. E.*; et al.

Physical Review B, 83(10), p.100504_1 - 100504_4, 2011/03

https://doi.org/10.1103/PhysRevB.83.100504

被引用回数：33 パーセンタイル：77.64(Materials Science, Multidisciplinary)

時間反転対称性(TRS)の破れた超伝導状態について調べるため、Pr(Os $_{1-x}$ Ru)Sb $_{12}$ とPr $_{1-y}$ LaOsSb $_{12}$ 合金において零磁場ミュオンスピン緩和測定を行った。TRSは自発的な局所磁場の発生で知ることができる。両合金において磁場は最初は減少したが、Ru置換系ではLa置換系に比べて50%速い現象がみられた。この結果から、TRSはで抑制されるが、La置換系ではすべての濃度において残ることが明らかになった。この結果は結晶場励起子によるクーパー対形成によるTRSの破れた超伝導機構を支持するものである。

論文

J-PARC muon facility, MUSE

三宅康博*; 下村浩一郎*; 河村成肇*; Strasser, P.*; 牧村俊助*; 幸田章宏*; 藤森寛*; 中原一隆*; 竹下聡史*; 小林庸男*; et al.

Journal of Physics; Conference Series, 225, p.012036_1 - 012036_7, 2010/06

https://doi.org/10.1088/1742-6596/225/1/012036

被引用回数：8 パーセンタイル：91.7

The science facility (MUSE) along with the neutron, hadron and neutrino facilities is one of the experimental areas PF the J-PARC project, which was approved for construction in a period from 2001 to 2008. Construction of the MLF building was started in the beginning of 2004, and was completed at the end of the 2006 fiscal year. On September 19th, 2008, the graphite target for muon production was placed into the 3 GeV proton beam line. On September 26th, 2008, we finally succeeded to extract surface muon beams. We also succeeded in the extraction of the decay muons on December 25th, 2008.

論文

J-PARC decay muon channel construction status

Strasser, P.*; 下村浩一郎*; 幸田章宏*; 河村成肇*; 藤森寛*; 牧村俊助*; 小林庸男*; 中原一隆*; 加藤峯夫*; 竹下聡史*; et al.

Journal of Physics; Conference Series, 225, p.012050_1 - 012050_8, 2010/06

https://doi.org/10.1088/1742-6596/225/1/012050

被引用回数：12 パーセンタイル：95.37

The new Muon Science Facility (MUSE) that is now under construction at J-PARC in the Materials and Life Sciences Facility (MLF) building will comprise four types of muon channels. In the first stage, a conventional superconducting decay muon channel (D-Line) was constructed, which can extract surface (positive) muons with an expected muon yield of /s and decay positive/negative muon up to 120 MeV/c, with an expected muon yield of a few /s at 60 MeV/c for both positive and negative muons. This channel will be used for various kinds of muon experiments like SR, muon catalyzed fusion and nondestruction elements analysis.

論文

Incommensurate spin correlations induced by magnetic Fe ions substituted into overdoped Bi $_{1.75}$ Pb $_{0.35}$ Sr $_{1.90}$ CuO $_{6+z}$

平賀晴弘*; 林陽一郎*; 脇本秀一; 武田全康; 加倉井和久; 足立匡*; 小池洋二*; 山田幾也*; 宮崎正範*; 平石雅俊*; et al.

Physical Review B, 81(14), p.144501_1 - 144501_6, 2010/04

https://doi.org/10.1103/PhysRevB.81.144501

被引用回数：15 パーセンタイル：55.59(Materials Science, Multidisciplinary)

Spin correlations in the overdoped region of Bi $_{1.75}$ Pb $_{0.35}$ Sr $_{1.90}$ CuO $_{6+z}$ have been explored with Fe-doped single crystals characterized by neutron scattering, muon-spin-rotation spectroscopy, and magnetic-susceptibility measurements. The incommensurability is unexpectedly large (0.2 r.l.u.), as compared with the overdoped La $_{2-x}$ Sr $_{x}$ CuO $_{4}$ . However, this large is close to the hole concentration . While our findings in Fe-doped Bi $_{1.75}$ Pb $_{0.35}$ Sr $_{1.90}$ CuO $_{6+z}$ support the commonality of incommensurate spin correlations in high- cuprate superconductors, they also suggest that the magnetic response might be dominated by a distinct mechanism in the overdoped region.

論文

Birth of an intense pulsed muon source, J-PARC MUSE

三宅康博*; 下村浩一郎*; 河村成肇*; Strasser, P.*; 牧村俊助*; 幸田章宏*; 藤森寛*; 中原一隆*; 門野良典*; 加藤峯夫*; et al.

Physica B; Condensed Matter, 404(5-7), p.957 - 961, 2009/04

https://doi.org/10.1016/j.physb.2008.11.227

被引用回数：11 パーセンタイル：45.79(Physics, Condensed Matter)

ミュオン科学実験施設(MUSE)はJ-PARCの実験施設の一つである、MUSEは中性子とミュオン利用の実験施設である物質生命科学実験施設(MLF)の中にある。MLFの建屋建設は2004年にはじまり、2006年度末に完了した。われわれはそこにビームライン機器の設置を行っており、最初のミュオンビームが2008年の秋に発生する予定である。

論文

Novel features in filled skutterudites containing rare-earth elements with a plural number of 4f-electrons

佐藤英行*; 青木勇二*; 菊地大輔*; 菅原仁*; 髭本亘; 大石一城; 伊藤孝; Heffner, R. H.; Saha, S. R.*; 幸田章宏*; et al.

Physica B; Condensed Matter, 404(5-7), p.749 - 753, 2009/04

https://doi.org/10.1016/j.physb.2008.11.182

被引用回数：5 パーセンタイル：25.9(Physics, Condensed Matter)

充填スクッテルダイト構造を持つ物質における強い電子相関に基づく現象は多岐に渡る。特に、複数の4f電子が含まれる場合は軌道の自由度が新たな非磁性又は弱磁性を伴う現象に大きな役割を果たす。Pr系及びSm系充填スクッテルダイト構造物質においてさまざまな例が見いだされており、これらとミュオンスピン緩和実験の関連を紹介する。

論文

J-PARCの拓く凝縮系科学

藤井保彦; 新井正敏; 門野良典*; 金谷利治*; 神山崇*; 新村信雄*; 野尻浩之*; 野田幸男*; 八木健彦*; 山田和芳*

固体物理, 43(7), p.441 - 450, 2008/07

http://ci.nii.ac.jp/naid/40016194703

平成20年12月から利用を開始するJ-PARC/MLF(中性子,ミュオン)において、凝縮系科学分野で計画している新しい科学を切り拓く研究を各分野の専門家がそれぞれの夢も交えて紹介している。

論文

SR measurements on the vortex lattice of CaAlSi; Anisotropic response in magnetic penetration depth

黒岩壮吾*; 佐藤宏樹*; 幸田章宏*; 門野良典*; 大石一城*; 髭本亘; 秋光純*

Journal of Physics and Chemistry of Solids, 68(11), p.2124 - 2128, 2007/11

https://doi.org/10.1016/j.jpcs.2007.08.048

被引用回数：3 パーセンタイル：18.16(Chemistry, Multidisciplinary)

六方晶の超伝導体CaAlSiの磁場侵入長及びコヒーレント長をミュオンスピン回転法により測定した。改訂ロンドンモデルによる解析の結果、面内の磁場侵入長は磁場とともに増大し、面間の磁場侵入長はほぼ一定であることを見いだした。この磁場依存性は磁場誘起準粒子励起を明確に示しており、CaAlSiは異方的なギャップ構造を持つことが提案される。

論文

Microscopic properties of vortex states in YB probed by muon spin rotation

門野良典*; 黒岩壮吾*; 秋光純*; 幸田章宏*; 大石一城; 髭本亘; 大谷茂樹*

Physical Review B, 76(9), p.094501_1 - 094501_11, 2007/09

https://doi.org/10.1103/PhysRevB.76.094501

被引用回数：10 パーセンタイル：44.94(Materials Science, Multidisciplinary)

The local magnetic field distribution B() in the mixed state of a boride superconductor, YB, is studied by muon spin rotation (SR). A comparative analysis using the modified London model and Ginzburg-Landau(GL) model indicates that the latter exhibits a better agreement with SR data at higher fields and thus demonstrating the importance of reproducing the field profile near the vortex cores when the inter vortexdistance becomes closer to the GL coherence length. The temperature and field dependence of the magnetic penetration depth () does not exhibit any indications of the nonlocal effect or of low-lying quasiparticle excitation. This suggests that the strong coupling of electrons to the rattling motion of Y ions in the boron cage, as suggested by bulk measurements, induces a conventional superconductivity with isotropic -wave pairing. Considering the present results, a review is provided for probing the anisotropy of the superconducting order parameters by the slope of against the field ().