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論文

Q dependence of magnetic resonance mode on FeTe $_{0.5}$ Se $_{0.5}$ studied by inelastic neutron scattering

石角元志*; 樹神克明; 梶本亮一; 中村充孝; 稲村泰弘; 池内和彦*; Ji, S.*; 新井正敏*; 社本真一

Condensed Matter (Internet), 4(3), p.69_1 - 69_10, 2019/09

https://doi.org/10.3390/condmat4030069

中性子非弾性散乱により観測された磁気共鳴モードのQ依存性という初めての手法で、FeTe $_{0.5}$ Se $_{0.5}$ の超伝導対称性がs波であることを実験的に示した。

論文

Status of neutron spectrometers at J-PARC

梶本亮一; 横尾哲也*; 中村充孝; 川北至信; 松浦直人*; 遠藤仁*; 瀬戸秀紀*; 伊藤晋一*; 中島健次; 河村聖子

Physica B; Condensed Matter, 562, p.148 - 154, 2019/06

https://doi.org/10.1016/j.physb.2018.11.061

Seven time-of-flight quasielastic/inelastic neutron scattering instruments are installed on six beamlines in the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (JPARC). Four of these instruments are chopper-type direct-geometry spectrometers, one is a near-backscattering indirect-geometry spectrometer, and the other two are spin-echo-type spectrometers. This paper reviews the characteristic features, recent scientific outcomes, and progress in development of MLF spectrometers.

論文

Study on use of superconducting magnet and first inelastic neutron scattering experiment under magnetic field at 4SEASONS spectrometer

梶本亮一; 石角元志*; 吉良弘*; 金子耕士; 中村充孝; 蒲沢和也*; 稲村泰弘; 池内和彦*; 飯田一樹*; 村井直樹; et al.

Physica B; Condensed Matter, 556, p.26 - 30, 2019/03

https://doi.org/10.1016/j.physb.2018.11.065

被引用回数：2 パーセンタイル：17.06(Physics, Condensed Matter)

Magnets are important for studying magnetism and are commonly used as sample environment devices of neutron scattering instruments. However, the use of magnets was prevented at the time-of-flight direct-geometry neutron spectrometer 4SEASONS in Materials and Life Science Experimental Facility (MLF) at J-PARC, because the instrument is surrounded by iron components, and it is equipped with a piece of equipment operated with magnetic bearings. In the present work, we investigate the influence of stray magnetic fields from a superconducting magnet which is shared among neutron scattering instruments in MLF. Based on the investigation, we modified 4SEASONS such that it can be used with the magnet. Finally, we successfully performed the first inelastic neutron scattering experiments with applied magnetic fields using this sample environment.

報告書

MLF将来計画技術検討会・中性子実験装置発表資料集

中島健次; Harjo, S.; 山田悟史*; 及川健一; 梶本亮一

JAEA-Review 2018-032, 43 Pages, 2019/02

JAEA-Review-2018-032.pdf:9.78MB

大強度陽子加速器施設(J-PARC)物質・生命科学実験施設(MLF)では2017年より「MLF将来計画技術検討会」が設置され、MLFの線源や実験装置の将来計画について議論が行われてきた。同検討会では中性子実験装置についても装置カテゴリ毎に現状の問題点や今後目指すべき方向性についての報告がなされた。本報告書は、今後の将来計画の検討の一助とするべく、同検討会におけるMLF中性子実験装置に関する発表資料をまとめたものである。

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

パーセンタイル：100(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.

報告書

Proceedings of the User Group Meeting on MLF Spectrometers (DIRECTION 2018); October 11, 2018, Ibaraki Quantum Beam Research Center (Tokai, Ibaraki, Japan)

梶本亮一; 横尾哲也*; 松浦直人*

JAEA-Review 2018-024, 78 Pages, 2019/01

JAEA-Review-2018-024.pdf:76.52MB

平成30年10月11日、MLF中性子分光器による合同のユーザーミーティング「DIRECTION 2018」がJ-PARC MLF、高エネルギー加速器研究機構物質構造科学研究所、総合科学研究機構の共催で開催された。本ミーティングは6つの分光器、すなわちBL01(4SEASONS)、BL02(DNA)、BL06(VIN ROSE)、BL12(HRC)、BL14(AMATERAS)、BL23(POLANO)におけるユーザー利用の活性化およびユーザーと装置の協力関係の構築を目指して開催されたものである。研究会では14件の口頭発表および21件のポスター発表が行われ、各装置を利用して行われた研究成果の紹介、各装置や試料環境に関する現状の報告がなされるとともに、装置や試料環境に関する要望や今後の展開等について密接な議論が交わされた。本報告書はこのミーティングの講演要旨および講演で使用された発表資料を収録したものである。

論文

High-energy magnetic excitations in lightly oxygen-doped lanthanum nickel oxides

中島健次; 梶本亮一

Physica B; Condensed Matter, 551, p.142 - 145, 2018/12

https://doi.org/10.1016/j.physb.2017.12.015

パーセンタイル：100(Physics, Condensed Matter)

We will report on magnetic excitations in lightly oxygen doped lanthanum nickel oxide, La $_{2}$ NiO $_{4+delta}$ . By introducing slightly excessive oxygen atoms in the system, magnetic excitations in La $_{2}$ NiO $_{4}$ drastically changes its picture. In lower energy region, spin-wave stiffness strongly suppressed. On the other hand, in the higher energy region, spin-wave dispersion curve is almost same as in the stoichiometric system, while excitations show considerable broadening. Alternation of the character of the excitations by changing energy is also reported in hole doped cuprates and cobalates. We consider that this behavior is one of key clues to understand magnetism and transport properties in carrier doped layered transition metal oxides. We investigated detail of magnetic excitations in two different lightly doped systems, La $_{2}$ NiO $_{4.02}$ and La $_{2}$ NiO $_{4.11}$ in wide momentum and energy transfer space by using time-of-flight spectrometers at J-PARC. Observed doping effects in magnetic excitations will be discussed by comparing them to those reported in other related layered transition metal oxides.

論文

Performances of oscillating radial collimator for the Fermi chopper spectrometer 4SEASONS at J-PARC

中村充孝; 神原理*; 飯田一樹*; 梶本亮一; 蒲沢和也*; 池内和彦*; 石角元志*; 青山和弘*

Physica B; Condensed Matter, 551, p.480 - 483, 2018/12

https://doi.org/10.1016/j.physb.2018.05.028

被引用回数：1 パーセンタイル：100(Physics, Condensed Matter)

近年、磁場や圧力、高温といった特殊環境下での中性子非弾性散乱実験へのニーズが高まっており、質の高いデータを得るためには試料環境機器からの不要な散乱をできる限り低く抑える必要がある。そこで、我々はユーザーのニーズに応えるため、J-PARCのフェルミチョッパー分光器四季に特化した揺動型ラジアルコリメータを開発した。四季では比較的高い入射エネルギーを用いることから、コリメータのブレード素材に水素フリーの金属シートを採用した。このラジアルコリメータの制御システムでは、揺動スピードや揺動角等といった揺動パターンを柔軟に変更することが可能である。本稿では、新たに開発したラジアルコリメータの性能と残された課題について報告する。

論文

High-energy spin fluctuation in low-T $_{c}$ iron-based superconductor LaFePO $_{0.9}$

石角元志*; 社本真一; 樹神克明; 梶本亮一; 中村充孝; Hong, T.*; Mutka, H.*

Scientific Reports (Internet), 8, p.16343_1 - 16343_6, 2018/11

https://doi.org/10.1038/s41598-018-33878-x

パーセンタイル：100(Multidisciplinary Sciences)

磁気揺らぎはBCS理論に従わない非従来型超伝導で最も可能性のある機構として重要な役割を担うと考えられてきた。今回、これまで磁気ゆらぎが見つかっていない5Kという低い超伝導転移温度の鉄リン系超伝導体LaFePO $_{0.9}$ で、30-50meVの高エネルギーで磁気ゆらぎを見つけた。これはこれまで考えられてきた高エネルギー磁気揺らぎで、高い超伝導転移温度になるという考えとは矛盾することから、超伝導機構の理解に向けて重要な発見である。

論文

Al-impurity-induced magnetic excitations in heavily over-doped La $_{1.7}$ Sr $_{0.3}$ Cu $_{0.95}$ Al $_{0.05}$ O $_{4}$

池内和彦*; 中島健次; 河村聖子; 梶本亮一; 脇本秀一; 鈴木謙介*; 藤田全基*

AIP Advances (Internet), 8(10), p.101318_1 - 101318_5, 2018/10

https://doi.org/10.1063/1.5043077

中性子散乱実験により、Al不純物を導入した実効ホール濃度0.25の銅酸化物超伝導体、La $_{1.7}$ Sr $_{0.3}$ Cu $_{0.95}$ Al $_{0.05}$ O $_{4}$ の巨大単結晶について、磁気励起を測定した。

論文

Schottky specific heat of the lightly Mn-substituted electron-doped SrTiO

奥田哲治*; 梶本亮一; 野田正亮*; 桑原英樹*

AIP Advances (Internet), 8(10), p.101339_1 - 101339_5, 2018/10

https://doi.org/10.1063/1.5042835

Large changes in the low-temperature specific heat (low-) by applying magnetic fields up to 9 Tesla were found in the lightly Mn-substituted electron-doped perovskites Sr $_{1-x}$ La $_{x}$ TiO $_{3}$ . The changes in the low- are qualitatively well explained by the Schottky specific heat ( $C_mathrm{Sch}$ ) of localized spins of the Mn 3d electrons in weak internal magnetic fields via itinerant electrons. According to the analysis by using the conventional model, the doped Mn ions are apparently not Mn $^{4+}$ ( = 3/2) ions, but are Jahn-Teller active Mn $^{3+}$ ( = 2) ions or mixtures of Mn $^{3+}$ and Mn $^{2+}$ ions. However, the actual numbers of localized spins estimated from $C_mathrm{Sch}$ are about 30% smaller than the expected values. Part of the localized spins of the Mn 3d electrons may disappear due to Kondo coupling with the itinerant electrons, leading to the observed enhancement of the electronic specific heat coefficients.

論文

Neutron inelastic scattering study of the -electron states in NdPdAl

目時直人; 山内宏樹; 鈴木博之*; 北澤英明*; 蒲沢和也*; 池内和彦*; 梶本亮一; 中村充孝; 稲村泰弘

Journal of the Physical Society of Japan, 87(8), p.084708_1 - 084708_7, 2018/08

https://doi.org/10.7566/JPSJ.87.084708

被引用回数：3 パーセンタイル：20.01(Physics, Multidisciplinary)

電子化合物NdPdAlの中性子散乱による研究を行った。0K, 35.4K, 88.3K, 101.5K, and 198.8Kの結晶場レベルを励起スペクトルから明らかにした。基底状態は主としての軌道によって構成され、これが大きな負の $B_{20}=-1.4$ Kと一軸異方性を生じる。結晶場から計算された磁気モーメント, 帯磁率, 磁化曲線, 比熱は実験をよく説明する。CePdAlやPrPdAlと共通した電荷分布の存在は同じ構造を持つアクチノイド化合物においても局在的な性質が重要で、UPdAlの局在5電子状態やNpPdAlの重い電子系超伝導にその価数の不安定性が重要な役割をすることを示している。

論文

Status report of the chopper spectrometer 4SEASONS

梶本亮一; 中村充孝; 稲村泰弘; 蒲沢和也*; 池内和彦*; 飯田一樹*; 石角元志*; 村井直樹; 吉良弘*; 中谷健; et al.

Journal of Physics; Conference Series, 1021(1), p.012030_1 - 012030_6, 2018/06

https://doi.org/10.1088/1742-6596/1021/1/012030

4SEASONS is a medium-resolution thermal neutron chopper spectrometer in the Materials and Life Science Experimental Facility (MLF) at J-PARC. Although 4SEASONS is routinely used for many experiments by internal and external users, upgrading and maintenance work is still underway. This paper reviews the recent improvements of the instrument.

論文

Effect of electron correlations on spin excitation bandwidth in Ba $_{0.75}$ K $_{0.25}$ Fe $_{2}$ As $_{2}$ as seen via time-of-flight inelastic neutron scattering

村井直樹; 鈴木雄大*; 出田真一郎*; 中島正道*; 田中清尚*; 池田浩章*; 梶本亮一

Physical Review B, 97(24), p.241112_1 - 241112_6, 2018/06

https://doi.org/10.1103/PhysRevB.97.241112

被引用回数：3 パーセンタイル：25.37(Materials Science, Multidisciplinary)

非弾性中性子散乱による鉄系超伝導体Ba $_{0.75}$ K $_{0.25}$ Fe $_{2}$ As $_{2}$ の磁気励起測定を行い、約200meV程度のバンド幅を持つスピン波的分散を観測した。測定されたスペクトルは、同一試料に対する角度分解光電子分光測定により得られた電子バンドの繰り込み因子を考慮し、密度汎関数理論により構築された5軌道ハバード模型に乱雑位相近似を適応する事で再現される。これらの結果は電子バンドの繰り込みという形でしばしば現れる所謂、電子相関効果の観測が非弾性中性子散乱によっても可能であることを示すものである。

論文

Odd and even modes of neutron spin resonance in the bilayer iron-based superconductor CaKFe $_{4}$ As $_{4}$

Xie, T.*; Wei, Y.*; Gong, D.*; Fennell, T.*; Stuhr, U.*; 梶本亮一; 池内和彦*; Li, S.*; Hu, J.*; Luo, H.*

Physical Review Letters, 120(26), p.267003_1 - 267003_7, 2018/06

https://doi.org/10.1103/PhysRevLett.120.267003

被引用回数：3 パーセンタイル：20.01(Physics, Multidisciplinary)

We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFeAs. In contrast to its quasi-two-dimensional electron structure, three strongly -dependent modes of spin resonance are found below = 35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper-pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high- superconducting families share a common nature.

論文

Elastic and dynamical structural properties of La and Mn-doped SrTiO $_{3}$ studied by neutron scattering and their relation with thermal conductivities

梶本亮一; 中村充孝; 村井直樹; 社本真一; 本田孝志*; 池田一貴*; 大友季哉*; 畑博人*; 江藤貴弘*; 野田正亮*; et al.

Scientific Reports (Internet), 8(1), p.9651_1 - 9651_8, 2018/06

https://doi.org/10.1038/s41598-018-27984-z

被引用回数：2 パーセンタイル：41.94(Multidisciplinary Sciences)

The electron-doped SrTiO $_{3}$ exhibits good thermoelectric properties, which makes this material a promising candidate of an n-type oxide thermoelectric device. Recent studies indicated that only a few percent co-doping of La and Mn in SrTiO $_{3}$ substantially reduces the thermal conductivity, thereby greatly improving the thermoelectric figure of merit at room temperature. Our time-of-flight neutron scattering studies revealed that by doping both La and Mn into SrTiO $_{3}$ , the inelastic scattering spectrum shows a momentum-independent increase in the low-energy spectral weight approximately below 10 meV. The increase in the low-energy spectral weight exhibits a clear correlation with thermal conductivity. The correlation is attributed to dynamical and local structural fluctuations caused by the Jahn-Teller instability in Mn $^{3+}$ ions coupled with the incipient ferroelectric nature of SrTiO $_{3}$ , as the origin of the low thermal conductivity.

論文

Instrumental resolution of the chopper spectrometer 4SEASONS evaluated by Monte Carlo simulation

梶本亮一; 佐藤研太朗*; 稲村泰弘; 藤田全基*

AIP Conference Proceedings 1969, p.050004_1 - 050004_8, 2018/05

https://doi.org/10.1063/1.5039301

We performed simulations of the resolution function of the 4SEASONS spectrometer at J-PARC by using the Monte Carlo simulation package McStas. The simulations showed reasonably good agreement with analytical calculations of energy and momentum resolutions by using a simplified description. We implemented new functionalities in Utsusemi, the standard data analysis tool used in 4SEASONS, to enable visualization of the simulated resolution function and predict its shape for specific experimental configurations.

論文

Magnetic excitations in the orbital disordered phase of MnVO

松浦慧介*; 佐賀山基*; 上原周*; 新居陽一*; 梶本亮一; 蒲沢和也*; 池内和彦*; Ji, S.*; 阿部伸行*; 有馬孝尚*

Physica B; Condensed Matter, 536, p.372 - 376, 2018/05

https://doi.org/10.1016/j.physb.2017.09.085

パーセンタイル：100(Physics, Condensed Matter)

We have investigated the temperature dependence of magnetic dynamics in a spinel-type vanadium oxide MnVO by inelastic neutron scattering. The scattering intensity of excitation around 20 meV disappears in the collinear intermediate-temperature cubic-ferrimagnetic phase, which reveals that this excitation should be peculiar to the orbital ordered phase. We have found a weakly dispersive mode emergent from a non-integer wavevector at 56 K, which lies in the cubic-ferrimagnetic phase between non-coplanar ferrimagnetic and paramagnetic phases. This indicates that the probable presence of an incommensurate instability in the simple collinear structure.

論文

Detailed study of the structure of the low-energy magnetic excitations in overdoped La $_{1.75}$ Sr $_{0.25}$ CuO $_{4}$

池内和彦*; 菊地龍弥*; 中島健次; 梶本亮一; 脇本秀一; 藤田全基*

Physica B; Condensed Matter, 536, p.717 - 719, 2018/05

https://doi.org/10.1016/j.physb.2017.11.022

被引用回数：1 パーセンタイル：63.1(Physics, Condensed Matter)

銅酸化物高温超伝導体の過剰ドープ領域における低エネルギーの磁気励起の構造の詳細を調べるために、我々は、La $_{1.75}$ Sr $_{0.25}$ CuO $_{4}$ の中性子非弾性散乱実験を行った。過去に報告されたように、非整合な磁気相関に対応した $Q_{rm tet}$ = (0.5 , 0.5)/(0.5, 0.5 )を中心とした磁気励起を明瞭に観測した。それに加えて、 $Q_{rm tet}=(0.5, 0.5)$ を中心とした円環状の励起も観測された。円環の半径(=0.109)は、磁気相関の非整合性(=0.118)より小さい。このことは、円環状の磁気励起は非整合な磁気相関とはその原因を異にしていることを示唆している。La $_{2-x}$ Sr $_{x}$ CuO $_{4}$ の磁気励起はこのように2種類の励起を持つことが示唆される。

論文

Fe-impurity-induced magnetic excitations in heavily over-doped La $_{1.7}$ Sr $_{0.3}$ Cu $_{0.95}$ Fe $_{0.05}$ O $_{4}$

池内和彦*; 菊地龍弥*; 中島健次; 梶本亮一; 脇本秀一; 藤田全基*

Journal of Physics; Conference Series, 969(1), p.012024_1 - 012024_5, 2018/04

https://doi.org/10.1088/1742-6596/969/1/012024

Inelastic neutron scattering experiments were performed to investigate the effect of Fe substitution on the magnetic excitation spectra in a heavily hole-doped cuprate system La $_{1.7}$ Sr $_{0.3}$ Cu $_{0.95}$ Fe $_{0.05}$ O $_{4}$ . Well-defined low-energy magnetic excitations, associated with a static magnetic order, were observed at the incommensurate (IC) positions. The incommensurability of 0.144 (r.l.u) was larger than that of 0.125 (r.l.u) in LSCO with = 0.25, suggesting an increase of incommensurability by Fe substitution. In addition to the obvious effect on IC excitations, we show the emergence of ring-shaped magnetic excitations by Fe-substitution. These results are incompatible with a simple pinning scenario of the stripe order, which is characterized by local spin correlations. The metallic aspect of the low-energy part of the magnetic excitation, which underlies high-temperature superconductivity in over-doped cuprate systems, would be enhanced/induced by Fe substitution.