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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

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

Invariant incommensurate coherence length in spin-density-wave excitation of Cr$$_{0.99}$$Fe$$_{0.01}$$

平賀 晴弘*; 矢野 真一郎*; 福田 竜生

Journal of Magnetism and Magnetic Materials, 469, p.629 - 632, 2019/01

 パーセンタイル:100(Materials Science, Multidisciplinary)

Low-energy magnetic excitation of spin-density wave (SDW) in a single crystal of Cr$$_{0.99}$$Fe$$_{0.01}$$ was measured using cold neutron triple-axis spectroscopy. Because of the unchanged incommensurability and the constant line width in 2.5 $$leqslanthbaromegaleqslant$$ 6 meV, the magnetic excitation could not be explained with a conventional dispersion of $$hbaromega_qpropto q$$. In this paper, we conjectured the presence of standing waves, which would be excited in local spin matrices. The effectively vertical dispersion was attributed to the longitudinal spin fluctuation in the spin matrices. A series of low-energy magnetic excitations in Cr alloys could be understood with the coexistence of the standing waves and progressive waves such as spin waves.

論文

Gapless magnetic excitation in a heavily electron-doped antiferromagnetic phase of LaFeAsO$$_{0.5}$$D$$_{0.5}$$

玉造 博夢*; 平賀 晴弘*; 池内 和彦*; 飯村 壮史*; 村場 善行*; 中村 充孝; 佐賀山 基*; 山浦 淳一*; 村上 洋一*; 倉本 義夫*; et al.

Physical Review B, 98(17), p.174415_1 - 174415_6, 2018/11

 被引用回数:1 パーセンタイル:100(Materials Science, Multidisciplinary)

中性子非弾性散乱実験によりLaFeAsO$$_{0.5}$$D$$_{0.5}$$の第二反強磁性母相におけるギャップレス磁気励起の研究を行った。実験の結果、他の鉄系超伝導の母物質とは異なり、LaFeAsO$$_{0.5}$$D$$_{0.5}$$では磁気励起ギャップが4Kもの非常に低い温度においてもなお観測されないことを見出した。このギャップレス励起はab面内の擬等方性に起因するものと理解され、バンド計算による先行研究の結果と一致する。さらに、この相での磁気励起強度はノンドープのLaFeAsOに比べてはるかに強いこと、及び、常磁性相においてもなおLaFeAsO$$_{0.5}$$D$$_{0.5}$$の磁気励起が存在することを見出した本研究の実験結果は、本系において電子ドープが局在性を増強すると主張する最近の研究結果を強く支持する。

論文

Effects of Fe doping on anomalous specific heat and XAFS oscillation in antiferromagnetic metal Mn$$_3$$Si

平賀 晴弘*; 大山 研司*; 小坂 昌史*; 松村 大樹

AIP Advances (Internet), 8(10), p.101424_1 - 101424_5, 2018/10

The specific heat of Mn$$_{3-x}$$Fe$$_x$$Si was measured over a wide temperature range. Aside from the lattice and electronic specific heat components, another component had a significant contribution to the specific heat at low temperatures in the case of $$x$$ = 0.2; however, its contribution decreased when $$x$$ = 1.0. It is observed that the net component was retained at temperatures significantly higher than $$T_N$$ for both $$x$$. The XAFS spectra of the Mn $$K$$-edge for $$x$$ = 0 not only indicated a smooth structure near the edge, but also an unusually small amplitude in the extended high energy region; however, these features disappeared with Fe doping. The specific heat and XAFS data were discussed interms of the charge degree of freedom or electronic inhomogeneity.

論文

偏極中性子

平賀 晴弘*; 山口 泰男*; 丸山 龍治; 奥 隆之; 猪野 隆*

波紋, 28(3), p.144 - 149, 2018/08

サイエンスの様々な分野において偏極中性子散乱の果たす役割は益々増大しており、J-PARC MLFでの偏極中性子ビーム利用の高度化のため原子力機構等では偏極スーパーミラーや$$^3$$Heスピンフィルターの高性能化に関する研究開発を進めている。本稿では、当該分野に馴染みのないMLFユーザーや当該分野の初心者を対象とし、中性子ビーム偏極手法の基本的な原理や研究開発の現状について総説する。

論文

Science from the initial operation of HRC

伊藤 晋一*; 横尾 哲也*; 益田 隆嗣*; 吉澤 英樹*; 左右田 稔*; 池田 陽一*; 井深 壮史*; 川名 大地*; 佐藤 卓*; 南部 雄亮*; et al.

JPS Conference Proceedings (Internet), 8, p.034001_1 - 034001_6, 2015/09

Since the installation of the High Resolution Chopper Spectrometer, HRC, experiments using the HRC are being conducted to observe the dynamics in wide range of physics. Scientific results during the period since the initial construction are summarized.

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

 被引用回数:62 パーセンタイル:3.79(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$$_x$$ ($$x sim 0.5$$), 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 $$x sim 0$$ and advanced at $$x sim 0.5$$ 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

Ni-substitution effects on the spin dynamics and superconductivity in La$$_{1.85}$$Sr$$_{0.15}$$CuO$$_{4}$$

松浦 直人*; 藤田 全基*; 平賀 晴弘*; 古府 麻衣子*; 木村 宏之*; 脇本 秀一; Perring, T. G.*; Frost, C. D.*; 山田 和芳*

Physical Review B, 86(13), p.134529_1 - 134529_8, 2012/10

 被引用回数:5 パーセンタイル:68.39(Materials Science, Multidisciplinary)

Systematic inelastic neutron scattering studies have been performed on La$$_{1.85}$$Sr$$_{0.15}$$Cu$$_{1-y}$$Ni$$_{y}$$O$$_{4}$$ in order to elucidate the microscopic mechanism of magnetic Ni impurity doping effects on spin dynamics and superconductivity. In contrast to Zn doping, which precipitates static or quasistatic spin correlations around dopant, Ni doping remarkably reduces $$E_{rm comme}$$, the minimum energy of the upward branch of the hourglass-shaped magnetic dispersion where a commensurate magnetic peak is observed. Ni doping at $$y sim 0.04$$ further reduces $$E_{rm comme}$$ to zero energy and broadens the distribution of $$E_{rm comme}$$, corresponding to the appearance of the normal state at base temperature ($$T sim 4$$ K) as well as the broadening of the superconducting transition.

論文

Electronic excitations around the substituted atom in La$$_2$$Cu$$_{1-y}$$N$$_y$$O$$_4$$ as seen via resonant inelastic X-ray scattering

石井 賢司; 筒井 健二; 池内 和彦*; Jarrige, I.; 水木 純一郎; 平賀 晴弘*; 山田 和芳*; 遠山 貴己*; 前川 禎通; 遠藤 康夫*; et al.

Physical Review B, 85(10), p.104509_1 - 104509_5, 2012/03

 被引用回数:3 パーセンタイル:79.94(Materials Science, Multidisciplinary)

We perform a resonant inelastic X-ray scattering (RIXS) study of Ni-substituted La$$_2$$CuO$$_4$$ and Cu-substituted La$$_2$$NiO$$_4$$.Resonantly enhanced charge-transfer excitations are successfully observed by tuning the incident photon energy to the $$K$$-edge of the substituted element. These excitations display a very weak momentum dependence, evidencing their local character. We find a shift in the energy of the onset edge of these features compared with the non-substituted compounds La$$_2$$CuO$$_4$$ and La$$_2$$NiO$$_4$$. This shift is quantitatively reproduced by exact diagonalization calculations of the RIXS spectra. RIXS is shown to be a powerful tool to probe the electronic states of substituted elements and to understand their interaction with surrounding atoms.

論文

Developments of in-situ SEOP polarized $$^{3}$$He neutron spin filter in Japan

吉良 弘; 坂口 佳史; 奥 隆之; 鈴木 淳市; 中村 充孝; 新井 正敏; 遠藤 康夫; Chang, L.-J.; 加倉井 和久; 有本 靖*; et al.

Journal of Physics; Conference Series, 294, p.012014_1 - 012014_5, 2011/06

 被引用回数:8 パーセンタイル:4.31

The pulsed neutron source of J-PARC has started to operate in 2008 in Japan. To study structure of magnetic material and soft matters, polarized neutron scattering techniques are very important and powerful tools. It is urgently necessary for us to develop neutron spin polarizers for pulsed neutron scattering experiments. So we began the development of the in-situ SEOP system aiming to use it as a NSF for incident beam polarization and polarization analysis. In previous test performed by Ino et al., the $$^{3}$$He polarization reached 50% and not saturated yet. After that experiment, we began improving the SEOP system by installing the high power laser diode, the prism beam splitter and optimizing the beam-transform optics. By using this improved system, we performed the polarization test at BL10 in J-PRC and achieved the $$^{3}$$He polarization of 73%. We keep improving this in-situ SEOP system aiming to use it s an incident neutron polarizer at J-PARC.

論文

Applications of $$^{3}$$He neutron spin filters on the small-angle neutron scattering spectrometer SANS-J-II

坂口 佳史; 吉良 弘; 奥 隆之; 篠原 武尚; 鈴木 淳市; 酒井 健二; 中村 充孝; 相澤 一也; 新井 正敏; 能田 洋平; et al.

Journal of Physics; Conference Series, 294(1), p.012017_1 - 012017_7, 2011/06

 被引用回数:2 パーセンタイル:25.19

A polarized $$^{3}$$He neutron spin filter has been applied to polarization analysis on the small-angle neutron scattering spectrometer SANS-J-II at JRR-3. Measurements were taken on silver behenate, which has several coherent peaks in the small-angle region with a background of spin incoherent hydrogen scattering. Here we demonstrate that the coherent and spin incoherent scattering were successfully separated by the polarization analysis using the $$^{3}$$He spin filter on the instrument.

論文

Structure of glasses for $$^{3}$$He neutron spin filter cells

坂口 佳史; 吉良 弘; 奥 隆之; 篠原 武尚; 鈴木 淳市; 酒井 健二; 中村 充孝; 鈴谷 賢太郎; 相澤 一也; 新井 正敏; et al.

Journal of Physics; Conference Series, 294(1), p.012004_1 - 012004_7, 2011/06

 被引用回数:1 パーセンタイル:42.06

In spin-exchange optical pumping, there is unknown excess relaxation, called the X-factor, that limits attainable $$^{3}$$He polarization. It is known that the X-factor depends on the glass containers. Hence, it is expected that there are cell-to-cell variations in microscopic structure among the cells and that these variations affect the attainable $$^{3}$$He polarization. However, microscopic structure of the glasses for $$^{3}$$He neutron spin filters has not been clarified yet. In this paper, we have performed precise X-ray diffraction measurements for the glasses at SPring-8 using synchrotron radiation. The structural differences are observed between several types of glasses, and also, between the GE180 glass pieces with different thermal treatment. Based on the results, the structural influence on the performance of $$^{3}$$He neutron spin filters is discussed.

論文

Development and test of SEOP neutron spin filter in Japan

吉良 弘; 坂口 佳史; 奥 隆之; 鈴木 淳市; 中村 充孝; 新井 正敏; 加倉井 和久; 遠藤 康夫; 有本 靖*; 猪野 隆*; et al.

Physica B; Condensed Matter, 406(12), p.2433 - 2435, 2011/06

 被引用回数:8 パーセンタイル:55.78(Physics, Condensed Matter)

Polarized neutron scattering techniques are very important and powerful tools to study the fundamental structures of magnetic materials and soft matters. $$^{3}$$He has a very large absorption cross section for only neutrons in opposite spin state to that of the $$^{3}$$He nucleus. The scattering cross section of $$^{3}$$He is small. These two features allow nuclear spin polarized $$^{3}$$He gas to work as a NSF. Compared with other spin filters such as Heusler alloys and magnetic supermirrors, the $$^{3}$$He gas NSF have following advantages: it can polarize various energy of neutron such as cold, thermal and hot neutrons, it can work for broadband neutrons and it can be used for wide area and large divergence neutron beams. These characteristics of polarized $$^{3}$$He are convenient in use with J-PARC as NSF. We began the development of the on beam SEOP system aiming to use it s a NSF for incident beam polarisation and polarisation analysis. In this paper, we report the current development of SEOP system in Japan.

論文

Research on glass cells for $$^{3}$$He neutron spin filters

坂口 佳史; 吉良 弘; 奥 隆之; 篠原 武尚; 鈴木 淳市; 酒井 健二; 中村 充孝; 鈴谷 賢太郎; 相澤 一也; 新井 正敏; et al.

Physica B; Condensed Matter, 406(12), p.2443 - 2447, 2011/06

Polarized $$^{3}$$He neutron spin filters have attracted much attention because of their available wide energy range for polarizing neutrons and their large solid-angle. To use $$^{3}$$He neutron spin filters for the experiments, it is necessary to produce glass cells with good quality. For this purpose, we made research on the glass cells from several aspects. Firstly, we investigated on the microscopic structure for several glasses by means of X-ray diffraction measurement and tried to find a good measure of evaluating the quality of the cells in terms of their structure. Secondly, we investigated on the glass window, which the laser beam passes through for optical pumping. Thirdly, the cells should be optimized for the polarized neutron scattering experiments and the background from the cells needs to be evaluated. The scattered intensity from the cell in small-angle neutron scattering will also be presented.

論文

Research on glass cells for $$^{3}$$He neutron spin filters

坂口 佳史; 吉良 弘; 奥 隆之; 篠原 武尚; 鈴木 淳市; 酒井 健二; 中村 充孝; 鈴谷 賢太郎; 相澤 一也; 新井 正敏; et al.

Physica B; Condensed Matter, 406(12), p.2443 - 2447, 2011/06

 被引用回数:1 パーセンタイル:92.65(Physics, Condensed Matter)

Glass cells play an important role in polarized $$^{3}$$He neutron spin filters. To evaluate the scattering and absorption contribution from glass cells during neutron scattering experiments, we measured small-angle scattering and neutron transmission in GE180 and other glasses. To pursue the possibility of being a structural influence on $$^{3}$$He spin relaxation in GE180 glass cells, we performed precise X-ray diffraction measurement using synchrotron radiation at SPring-8. From these measurements, a structural difference was observed among GE180 glasses with different thermal treatments.

論文

Characterization of glasses for $$^{3}$$He neutron spin filter cells

坂口 佳史; 吉良 弘; 奥 隆之; 篠原 武尚; 鈴木 淳市; 酒井 健二; 中村 充孝; 鈴谷 賢太郎; 新井 正敏; 武田 全康; et al.

Nuclear Instruments and Methods in Physics Research A, 634(1, Suppl.), p.S122 - S125, 2011/04

Polarized $$^{3}$$He neutron spin filters are promising neutron polarizers in polarized neutron scattering experiments at facilities with two-dimensional detectors and pulsed neutron source. Although they are now operational at several institutions, it is still desired to be developed. Among required factors for the development, the study on the glasses in the filters is one of the important issues. In this paper, we report our recent investigation on the glass cells such as X-ray diffraction measurements and the measurements of the degree of circular polarization of the transmitted laser light through the glass window in the filter.

論文

Resonant inelastic X-ray scattering of La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$

石井 賢司; 池内 和彦*; Jarrige, I.; 水木 純一郎; 平賀 晴弘*; 山田 和芳*; 筒井 健二; 遠山 貴己*; 前川 禎通*; 遠藤 康夫*; et al.

Physica C, 470(Suppl.1), p.S155 - S157, 2010/12

 パーセンタイル:100(Physics, Applied)

Substitution of a specific element for a component is often used to elucidate its role in the superconductors. For a complete understanding of the substitution effect not only on the superconductivity but also on the electronic states, element-selective experiments are required. In this respect, resonant inelastic X-ray scattering (RIXS) has proven to be a powerful experimental technique enabling element-selective diagnosis of charge excitations. By tuning the incident photon energy to a given absorption edge of the element, the excitations involving the element are resonantly enhanced. In addition, RIXS has the advantage that momentum dependence can be measured. Using RIXS, we have measured the electronic excitations at the substituting sites in La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$ and La$$_2$$Ni$$_{0.95}$$Cu$$_{0.05}$$O$$_4$$. Near the absorption edge of the substituting element, namely the Ni $$K$$-edge for La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$ and the Cu $$K$$-edge for La$$_2$$Ni$$_{0.95}$$Cu$$_{0.05}$$O$$_4$$, charge transfer excitations from the 2$$p$$ level of neighboring oxygen to the upper Hubbard band of the substituted Ni/Cu are observed. Experimental spectra are qualitatively reproduced by a theoretical calculation based on a $$d$$-$$p$$ model.

論文

Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in Bi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$Cu$$_{0.91}$$Fe$$_{0.09}$$O$$_{6+y}$$

脇本 秀一; 平賀 晴弘*; 工藤 一貴*; 岡本 大地*; 西崎 輝一*; 加倉井 和久; Hong, T.*; Zheludev, A.*; Tranquada, J. M.*; 小林 典男*; et al.

Physical Review B, 82(6), p.064507_1 - 064507_7, 2010/08

 被引用回数:7 パーセンタイル:59.2(Materials Science, Multidisciplinary)

銅酸化物高温超伝導体にホールを過剰にドープされた系であり、かつ鉄磁性不純物をドープしたBi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$Cu$$_{0.91}$$Fe$$_{0.09}$$O$$_{6+y}$$における鉄誘起短距離磁気相関と電気抵抗の磁場依存性を調べた。その結果、電気抵抗は低温でlog(1/T)の依存性を示し、磁場中では負の電気磁気効果を示した。また短距離磁気相関は磁場により弱められる傾向を示した。これらの結果から、この系における鉄磁性不純物は金属中の希釈スピン系として振る舞い、近藤効果を示し、短距離磁気相関はRKKY相互作用からくることを明らかにした。このような遍歴スピンの振る舞いは低ホール濃度領域のストライプ状態に代表される局在スピンの振る舞いと異なり、超伝導の強い最適ドープ付近での両者の2面性を持つことを示唆する。

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

 被引用回数:14 パーセンタイル:38.99(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 $$delta$$ is unexpectedly large ($$sim$$0.2 r.l.u.), as compared with the overdoped La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$. However, this large $$delta$$ is close to the hole concentration $$p$$. 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-$$T_c$$ cuprate superconductors, they also suggest that the magnetic response might be dominated by a distinct mechanism in the overdoped region.

論文

Fe-doping effects on magnetism in hole-type superconductors of (Bi,Pb)$$_{2}$$Sr$$_{2}$$CuO$$_{6}$$

平賀 晴弘*; 脇本 秀一; 武田 全康; 加倉井 和久; 松村 大樹; 西畑 保雄; 水木 純一郎; 山田 和芳*

Journal of Physics; Conference Series, 200, p.012059_1 - 012059_4, 2010/02

 パーセンタイル:100

Bi$$_{1.75}$$Pb$$_{0.35}$$Sr$$_{1.90}$$CuO$$_{6+delta'}$$に対してFeドーピングがスピン相関に与える影響を探った。磁気効果による中性子非弾性散乱がincommensurateな位置に観測され、その性質がオーバードープ相においてLa$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$とは異なることがわかった。オーバードープ相での異常を動的ストライプモデルから考察した。

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