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論文

Generation of particles and fragments by quasicontinuous wave fiber laser irradiation of stainless steel, alumina, and concrete materials

大道 博行*; 山田 知典; 古河 裕之*; 伊藤 主税; 宮部 昌文; 柴田 卓弥; 長谷川 秀一*

Journal of Laser Applications, 33(1), p.012001_1 -  012001_16, 2021/02

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

In order to preserve a safe working environment, in particular for nuclear decommissioning like the Fukushima Daiichi Nuclear Power Station, special care should be taken to confine and retrieve such particles during laser processing. In the experiments, particle production from the vapor, as well as the molten phase layer in the targeted material were observed with a high speed camera with fine particles collected and analyzed using an electron microscope. The observed results were qualitatively interpreted with the help of a simplified one-dimensional hydrodynamic code coupled with a stress computation code. Characterization and classification of the results are expected to provide a useful database which will contribute to the decommissioning of nuclear facilities as well as other industrial applications.

論文

Gas barrier properties of chemical vapor-deposited graphene to oxygen imparted with sub-electronvolt kinetic energy

小川 修一*; 山口 尚人*; Holby, E. F.*; 山田 貴壽*; 吉越 章隆; 高桑 雄二*

Journal of Physical Chemistry Letters (Internet), 11(21), p.9159 - 9164, 2020/11

 被引用回数:2 パーセンタイル:42.52(Chemistry, Physical)

原子レベルで薄いグラフェン層は軽量であり、酸素などの腐食反応物質を直接ブロックする表面保護膜としての活用が提案されている。しかし、数十年という長期的な保護が望まれていることや、合成された実際のグラフェンには欠陥が存在するため、保護膜としての有用性は不明である。本研究では、酸素分子に運動エネルギーを与えることで、本来不浸透であるはずのグラフェンに対して、サブeVの運動エネルギーを持つ高速酸素分子では触媒的な浸透特性を示すことを実証した。この分子は熱分布のごく一部であるため、この暴露実験は数十年にわたる暴露を理解するための加速ストレステストとしての役割を果たす。グラフェンの透過率は、低速酸素分子と比較して2桁の増加を示した。また、グラフェンは、高速酸素分子が透過した後も、低速酸素分子に対する相対的な不透過性を維持しており、このプロセスが非破壊的であり、暴露された物質の基本的な特性であることを示している。

論文

Scaling of memories and crossover in glassy magnets

Samarakoon, A. M.*; 高橋 満*; Zhang, D.*; Yang, J.*; 片山 尚幸*; Sinclair, R.*; Zhou, H. D.*; Diallo, S. O.*; Ehlers, G.*; Tennant, D. A.*; et al.

Scientific Reports (Internet), 7(1), p.12053_1 - 12053_8, 2017/09

AA2017-0448.pdf:3.45MB

 被引用回数:4 パーセンタイル:44.41(Multidisciplinary Sciences)

Glassiness is ubiquitous and diverse in characteristics in nature. Understanding their differences and classification remains a major scientific challenge. Here, we show that scaling of magnetic memories with time can be used to classify magnetic glassy materials into two distinct classes. The systems studied are high temperature superconductor-related materials, spin-orbit Mott insulators, frustrated magnets, and dilute magnetic alloys. Our bulk magnetization measurements reveal that most densely populated magnets exhibit similar memory behavior characterized by a relaxation exponent of $$1-n$$ $$approx$$ $$0.6$$(1). This exponent is different from $$1-n$$ $$approx$$ $$1/3$$ of dilute magnetic alloys that was ascribed to their hierarchical and fractal energy landscape, and is also different from $$1-n=1$$ of the conventional Debye relaxation expected for a spin solid, a state with long range order.

論文

Detection of molecular oxygen adsorbate during room-temperature oxidation of Si(100)2$$times$$1 surface; In situ synchrotron radiation photoemission study

吉越 章隆; 山田 洋一*; 多賀 稜*; 小川 修一*; 高桑 雄二*

Japanese Journal of Applied Physics, 55(10), p.100307_1 - 100307_4, 2016/09

 被引用回数:1 パーセンタイル:6.36(Physics, Applied)

Si(100)2$$times$$1表面の室温酸化中の分子状吸着酸素を放射光光電子分光によって初めて検出することに成功した。O1sスペクトルはSi(111)7$$times$$7の場合と類似であった。分子状酸素は初期酸化物が生じた後に観測されたので、清浄表面上の解離酸素吸着に対する前駆状態でないことがわかった。この事実から我々は、2つのバックボンドにそれぞれ酸素原子をひとつずつ有する酸化Si原子上に分子状酸素が存在するとするモデルを提示する。

論文

Valence-band electronic structure evolution of graphene oxide upon thermal annealing for optoelectronics

山口 尚人*; 小川 修一*; 渡辺 大輝*; 穂積 英彬*; Gao, Y.*; 江田 剛輝*; Mattevi, C.*; 藤田 武志*; 吉越 章隆; 石塚 眞治*; et al.

Physica Status Solidi (A), 213(9), p.2380 - 2386, 2016/09

 被引用回数:8 パーセンタイル:46.1(Materials Science, Multidisciplinary)

本論文では加熱による酸化グラフェンの還元過程について報告する。酸化グラフェンにおいて酸素官能基の修飾度合いは加熱温度により制御できるため、加熱温度による価電子帯構造の変化をリアルタイム光電子分光で調べた。600$$^{circ}$$C以上の加熱により、フェルミ準位近傍の状態密度の顕著な増加が確認された。この結果は、600$$^{circ}$$Cにおいてバンドギャップが存在する酸化グラフェンからギャップが存在しない酸化グラフェンへと変化したことを示している。この成果は酸化グラフェンの光電子工学への応用を期待させるものである。

論文

Neutron scattering study of spin fluctuations in La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ by four-dimensional mapping of neutron cross-sections using the 4SEASONS chopper spectrometer

脇本 秀一; 池内 和彦*; 新井 正敏; 藤田 全基*; 梶本 亮一; 川村 奨*; 松浦 直人*; 中島 健次; 山田 和芳*

JPS Conference Proceedings (Internet), 8, p.034013_1 - 034013_6, 2015/09

Previous neutron results of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ (LSCO) by TOF measurements revealed that magnetic dynamical structure factor has a maximum at $$sim$$ 18 meV. To clarify the origin of the maximum, we carried out 4 dimensional mapping of dynamical structure factor $$S(Q, omega)$$ to see details of both magnons and phonons. We found that $$x$$ = 0 shows ordinary spin waves while $$x$$ = 0.08 shows a maximum at $$sim$$ 18 meV where $$Q$$-independent phonon branch crosses. This imply that in superconducting compositions phonon may also indirectly related to the superconductivity.

論文

Graphene growth and carbon diffusion process during vacuum heating on Cu(111)/Al$$_{2}$$O$$_{3}$$ substrates

小川 修一*; 山田 貴壽*; 石塚 眞治*; 吉越 章隆; 長谷川 雅考*; 寺岡 有殿; 高桑 雄二*

Japanese Journal of Applied Physics, 52(11), p.110122_1 - 110122_8, 2013/11

 被引用回数:17 パーセンタイル:63.5(Physics, Applied)

In this study, behavior of carbon atoms in annealing/cooling process of graphene/Cu(111) substrates is investigated using photoelectron spectroscopy and secondary ion mass spectrometry. After growth of graphene on Cu(111) surfaces, Cu$$_{2}$$O was formed at the graphene/Cu interface during transportation through the atmosphere. The Cu$$_{2}$$O layer completely disappeared by vacuum annealing at 773 K. Graphene was decomposed and carbon atoms diffuse into the Cu substrate by elevation of temperature up to 1223 K. When the sample was cooled down, the carbon atoms did not segregate on the surface and remain in the Cu substrate. This result indicates the carbon atoms easily diffuse into Cu substrates in vacuum annealing while the amount of diffused carbon atoms in the chemical vapor deposition (CVD) process is smaller, suggesting that the barrier layer which prevents from the diffusion of C atoms exists on Cu surfaces at the graphene CVD growth.

論文

Resonant inelastic X-ray scattering study of intraband charge excitations in hole-doped high-$$T_c$$ cuprates

脇本 秀一; 石井 賢司; 木村 宏之*; 池内 和彦*; 吉田 雅洋*; 足立 匡*; Casa, D.*; 藤田 全基*; 福永 靖*; Gog, T.*; et al.

Physical Review B, 87(10), p.104511_1 - 104511_7, 2013/03

 被引用回数:9 パーセンタイル:44.68(Materials Science, Multidisciplinary)

We have performed resonant inelastic X-ray scattering (RIXS) near the Cu-$$K$$ edge on various cuprate superconductors, covering underdoped to heavily overdoped regimes and focusing on charge excitations inside the charge-transfer gap. RIXS measurements with $$E_i$$= 9.003 keV on metallic La$$_{1.7}$$Sr$$_{0.3}$$CuO$$_{4}$$ and Bi$$_{1.76}$$Pb$$_{0.35}$$Sr$$_{1.89}$$CuO$$_{6+delta}$$ exhibit a dispersive intraband excitation below 4 eV, similar to that observed in the electron-doped Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_{4}$$. This is the first observation of a dispersive intraband excitation in a hole-doped system, evidencing that both electron- and hole-doped systems have a similar dynamical charge correlation function.

論文

Vacuum annealing formation of graphene on diamond C(111) surfaces studied by real-time photoelectron spectroscopy

小川 修一*; 山田 貴壽*; 石塚 眞治*; 吉越 章隆; 長谷川 雅考*; 寺岡 有殿; 高桑 雄二*

Japanese Journal of Applied Physics, 51(11), p.11PF02_1 - 11PF02_7, 2012/11

 被引用回数:23 パーセンタイル:70.04(Physics, Applied)

To clarify the graphene formation process on a diamond C(111) surface, changes in the chemical bonding states by annealing in vacuum were investigated by photoelectron spectroscopy using synchrotron radiation. It is difficult to study the formation of sp$$_{2}$$-bonded carbon atoms on a diamond C(111) surface because the peak of the sp$$_{2}$$ component overlaps the peak of the surface sp$$_{3}$$ component as a result of the 2$$times$$1 reconstruction. Therefore, we focused on the shift in the C 1s photoelectron spectra and energy loss spectra caused by band bending depending on the temperature. As a result, we found that graphitization on the diamond C(111) surface began at approximately 1120 K, which was lower than that for an SiC substrate. The photoelectron spectra indicated that a buffer layer composed of sp$$_{2}$$-bonded carbon atoms existed at the interface between the graphene and diamond C(111) surface.

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:6 パーセンタイル:31.07(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

リアルタイム光電子分光によるグラフェン・オン・ダイヤモンド形成過程の観察

小川 修一*; 山田 貴壽*; 石塚 眞治*; 渡辺 大輝*; 吉越 章隆; 長谷川 雅考*; 寺岡 有殿; 高桑 雄二*

表面科学, 33(8), p.449 - 454, 2012/08

絶縁膜上グラフェンの形成は次世代カーボントランジスタ作製に不可欠である。グラフェンの下地絶縁膜として、バンドギャップや絶縁破壊電圧がSiCよりも大きいダイヤモンドが注目されているが、非破壊でダイヤモンド表面のグラフェン形成を評価することが難しいため、ダイヤモンド表面におけるグラフェン形成過程は未だ明らかになっていない。そこで本研究ではバンドベンディングによる光電子スペクトルのシフトに着目し、グラフェン形成過程を調べた。その結果、ダイヤモンドC(111)表面のグラファイト化は約1120K以上で進行することがわかった。この温度はSiC(0001)表面におけるグラフェン形成温度よりも低温である。また、グラフェン/ダイヤモンド界面には遷移層が存在することが確認された。

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:3 パーセンタイル:17.85(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

The Fermi chopper spectrometer 4SEASONS at J-PARC

梶本 亮一; 中村 充孝; 稲村 泰弘; 水野 文夫; 中島 健次; 河村 聖子; 横尾 哲也*; 中谷 健; 丸山 龍治; 曽山 和彦; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB025_1 - SB025_6, 2011/01

 被引用回数:71 パーセンタイル:92.29(Physics, Multidisciplinary)

4SEASONS is a Fermi chopper spectrometer, which is in operation in Materials and Life Science Experimental Facility (MLF), J-PARC. It is intended to provide high-efficiency measurement of weak inelastic signals on novel spin and lattice dynamics with thermal neutrons. For this purpose, the spectrometer utilizes the coupled moderator and advanced instrumental design such as an elliptic-shaped converging neutron guide with high-critical angle supermirrors inside, long (2.5 m) position sensitive detectors, and a Fermi chopper feasible for multiple-incident-energy (multi-$$E_{rm i}$$) measurement with the repetition rate multiplication technique. Here we show detailed design of the spectrometer, evaluation of its performance, and some examples of measurements.

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:36.48(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:15 パーセンタイル:57.93(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

 被引用回数:0 パーセンタイル:0.04

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。

論文

Crossover from coherent quasiparticles to incoherent hole carriers in underdoped cuprates

橋本 信*; 吉田 鉄平*; 田中 清尚*; 藤森 淳*; 奥沢 誠*; 脇本 秀一; 山田 和芳*; 掛下 照久*; 永崎 洋*; 内田 慎一*

Physical Review B, 79(14), p.140502_1 - 140502_4, 2009/04

 被引用回数:13 パーセンタイル:52.72(Materials Science, Multidisciplinary)

In underdoped cuprates, only a portion of the Fermi surface survives as Fermi arcs due to pseudogap opening. In hole-doped La$$_{2}$$CuO$$_{4}$$, we have deduced the "coherence temperature" $$T_{coh}$$ of quasiparticles on the Fermi arc above which the broadened leading edge position in angle-integrated photoemission spectra is shifted away from the Fermi level and the quasiparticle concept starts to lose its meaning. $$T_{coh}$$ is found to rapidly increase with hole doping, an opposite behavior to the pseudogap temperature $$T^{*}$$. The superconducting dome is thus located below both $$T^{*}$$ and $$T_{coh}$$, indicating that the superconductivity emerges out of the coherent Fermionic quasiparticles on the Fermi arc. $$T_{coh}$$ remains small in the underdoped region, indicating that incoherent charge carriers originating from the Fermi arc are responsible for the apparently metallic transport at high temperatures.

論文

Charge excitations in the stripe-ordered La$$_{5/3}$$Sr$$_{1/3}$$NiO$$_{4}$$ and La$$_{2-x}$$(Ba,Sr)$$_{x}$$CuO$$_{4}$$ superconducting compounds

脇本 秀一; 木村 宏之*; 石井 賢司; 池内 和彦; 足立 匡*; 藤田 全基*; 加倉井 和久; 小池 洋二*; 水木 純一郎; 野田 幸男*; et al.

Physical Review Letters, 102(15), p.157001_1 - 157001_4, 2009/04

 被引用回数:24 パーセンタイル:76.17(Physics, Multidisciplinary)

Charge excitations in stripe-ordered 214 compounds, La$$_{5/3}$$Sr$$_{1/3}$$NiO$$_{4}$$ and 1/8-doped La$$_{2-x}$$(Ba, Sr)$$_{x}$$CuO$$_{4}$$ are studied using resonant inelastic X-ray scattering in hard X-ray regime. We are observing $$simeq 1$$ eV excitations with the momentum transfer corresponding to the charge stripe spatial period both for the diagonal (nickelate) and parallel (cuprates) stripes. They are interpreted as collective stripe excitations or anomalous softening of the charge excitonic modes of the in-gap states.

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