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論文

Structural, magnetic, transport, and thermoelectric properties of the pseudobrookite AlTi $_{2}$ O $_{5}$ -Ti $_{3}$ O $_{5}$ system

高濱隆成*; 石井透依*; 犬童代梧*; 有薗実駿*; 寺倉千恵子*; 十倉好紀*; 竹下直*; 野田正亮*; 桑原英樹*; 斎木琢夫*; et al.

Physical Review Materials (Internet), 4(7), p.074401_1 - 074401_11, 2020/07

https://doi.org/10.1103/PhysRevMaterials.4.074401

被引用回数：0 パーセンタイル：100(Materials Science, Multidisciplinary)

We investigated the structural, magnetic, transport, and high-temperature thermoelectric properties of single crystals of the pseudobrookite Al $_{1-x}$ Ti $_{2+x}$ O $_{5}$ for grown using a floating zone. We found a correlation of spin-singlet Ti $^{3+}$ -Ti $^{3+}$ dimers coupled with the lattice even in the conductive and phases which develops with increasing . This developing dimer correlation reduces the number of unpaired Ti $^{3+}$ ions, which makes the compound more conductive owing to the suppression of disorder for up to about 0.75. The dimer fluctuation causes a critical enhancement of the magnetic susceptibility at around 150 K in the phase near the boundary () between the and the phases. Such a correlation of the spin-singlet Ti $^{3+}$ -Ti $^{3+}$ dimers may produce a high Seebeck coefficient in the conductive and phases leading to a large thermoelectric power factor at high temperatures.

論文

Evidence for magnon-phonon coupling in the topological magnet Cu $_{3}$ TeO $_{6}$

Bao, S.*; Cai, Z.*; Si, W.*; Wang, W.*; Wang, X.*; Shangguan, Y.*; Ma, Z.*; Dong, Z.-Y.*; 梶本亮一; 池内和彦*; et al.

Physical Review B, 101(21), p.214419_1 - 214419_8, 2020/06

https://doi.org/10.1103/PhysRevB.101.214419

被引用回数：0 パーセンタイル：100(Materials Science, Multidisciplinary)

We perform thermodynamic and inelastic neutron scattering (INS) measurements to study the lattice dynamics (phonons) of a cubic collinear antiferromagnet Cu $_{3}$ TeO $_{6}$ which hosts topological spin excitations (magnons). While the specific heat and thermal conductivity results show that the thermal transport is dominated by phonons, the deviation of the thermal conductivity from a pure phononic model indicates that there is a strong coupling between magnons and phonons. In the INS measurements, we find a mode in the excitation spectra at 4.5 K, which exhibits a slight downward dispersion around the Brillouin zone center. This mode disappears above the Nel temperature and thus cannot be a phonon. Furthermore, the dispersion is distinct from that of a magnon. Instead, it can be explained by the magnon-polaron mode, collective excitations resulting from the hybridization between magnons and phonons. We consider the suppression of the thermal conductivity and emergence of the magnon-polaron mode to be evidence for magnon-phonon coupling in Cu $_{3}$ TeO $_{6}$ .

論文

Horizontal line nodes in SrRuO proved by spin resonance

飯田一樹*; 古府麻衣子; 鈴木雄大*; 村井直樹; 河村聖子; 梶本亮一; 稲村泰弘; 石角元志*; 長谷川舜介*; 増田隆嗣*; et al.

Journal of the Physical Society of Japan, 89(5), p.053702_1 - 053702_5, 2020/05

https://doi.org/10.7566/JPSJ.89.053702

被引用回数：1 パーセンタイル：24.83(Physics, Multidisciplinary)

We investigated the low-energy incommensurate (IC) magnetic fluctuations in SrRuO by the high-resolution inelastic neutron scattering measurements and random phase approximation (RPA) calculations. We observed a spin resonance with energy of $hbar omega_{rm res}0.56$ meV centered at a characteristic wavevector $Q_{rm res}=(0.3,0.3,0.5)$ . The resonance energy corresponds well to the superconducting gap 2 = 0.56 meV estimated by the tunneling spectroscopy. The spin resonance shows the modulation with a maximum at around . The modulated intensity of the spin resonance and our RPA calculations indicate that the superconducting gaps regarding the quasi-one-dimensional and sheets at the Fermi surfaces have the horizontal line nodes. These results may set a strong constraint on the pairing symmetry of SrRuO. We also discuss the implications on possible superconducting order parameters.

論文

The -electron state of the heavy fermion superconductor NpPdAl and the isostructural family

目時直人; Aczel, A. A.*; 青木大*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; 萩原正人*; Hong, T.*; 芳賀芳範; 池内和彦*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03

https://doi.org/10.7566/JPSCP.30.011123

希土類(4)やアクチノイド(5)は、電子数の増加とともに複雑さを増し、様々な相互作用が競合して多様な状態が出現する。多体電子系の結晶場分裂はバンド幅より狭いため、(1)高分解能の実験が必要で、(2)遍歴的なCeやU化合物は本質的に明瞭なスペクトルを示さない。また、(3)国際規制物質NpやPuなど超アクチノイド元素の取り扱いは厳しく規制されている。そこで比較的局在性の強い物質や希土類関連物質の、中性子散乱実験による磁気励起の研究が有益である。本稿では重い電子系化合物NpPdAlと関連物質の電子状態について述べる。

論文

Strong local moment antiferromagnetic spin fluctuations in V-doped LiFeAs

Xu, Z.*; Dai, G.*; Li, Y.*; Yin, Z.*; Rong, Y.*; Tian, L.*; Liu, P.*; Wang, H.*; Xing, L.*; Wei, Y.*; et al.

npj Quantum Materials (Internet), 5(1), p.11_1 - 11_7, 2020/02

https://doi.org/10.1038/s41535-020-0212-x

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

We use neutron scattering to study Vanadium (hole)-doped LiFe $_{1-x}$ V $_{x}$ As. In the undoped state, LiFeAs exhibits superconductivity at $T_mathrm{c} = 18$ K and transverse incommensurate spin excitations similar to electron overdoped iron pnictides. Upon Vanadium doping to form LiFe $_{0.955}$ V $_{0.045}$ , the transverse incommensurate spin excitations in LiFeAs transform into longitudinally elongated ones in a similar fashion to that of potassium (hole)-doped Ba $_{0.7}$ K $_{0.3}$ Fe $_{2}$ As $_{2}$ but with dramatically enhanced magnetic scattering and elimination of superconductivity. This is different from the suppression of the overall magnetic excitations in hole-doped BaFe $_{2}$ As $_{2}$ and the enhancement of superconductivity near optimal hole doping. These results are consistent with density function theory plus dynamic mean field theory calculations, suggesting that Vanadium doping in LiFeAs may induce an enlarged effective magnetic moment $S_mathrm{eff}$ with a spin crossover ground state arising from the inter-orbital scattering of itinerant electrons.

論文

Experimental investigation of the suppressed superconducting gap and double-resonance mode in Ba $_{1-x}$ K $_{x}$ Fe $_{2}$ As $_{2}$

出田真一郎*; 村井直樹; 中島正道*; 梶本亮一; 田中清尚*

Physical Review B, 100(23), p.235135_1 - 235135_7, 2019/12

https://doi.org/10.1103/PhysRevB.100.235135

被引用回数：0 パーセンタイル：100(Materials Science, Multidisciplinary)

Ba $_{1-x}$ K $_{x}$ Fe $_{2}$ As $_{2}$ has an exotic physical property where that the C $_{2}$ -SDW phase suddenly changes to the C $_{4}$ -magnetic phase and superconductivity is suppressed within a narrow composition range around x = 0.25. We have investigated the doping dependence of the electronic structure of Ba $_{1-x}$ K $_{x}$ Fe $_{2}$ As $_{2}$ using angle-resolved photoemission spectroscopy (ARPES) and found an anomaly in the superconducting (SC) gap structure only for x = 0.25 in both the hole and electron Fermi surfaces (FSs). We also propose that the mechanism of a newly observed double-resonance peak by inelastic neutron scattering is understandable by the SC gap obtained by ARPES. Our discovery reveals the important relationship between the C $_{4}$ - magnetic phase and superconductivity, and provides an opportunity to survey the underlying relationship between the SC gap and resonance mode in the hole-doped iron-based superconductor.

論文

Crystal structures of highly hole-doped layered perovskite nickelate Pr $_{2-x}$ Sr $_{x}$ NiO $_{4}$ studied by neutron diffraction

梶本亮一; 中島健次; 藤田全基*; 石角元志*; 鳥居周輝*; 石川喜久*; Miao, P.*; 神山崇*

Journal of the Physical Society of Japan, 88(11), p.114602_1 - 114602_6, 2019/11

https://doi.org/10.7566/JPSJ.88.114602

被引用回数：0 パーセンタイル：100(Physics, Multidisciplinary)

A high-resolution time-of-flight powder neutron diffraction study of the layered nickel oxide Pr $_{2-x}$ Sr $_{x}$ NiO $_{4}$ with and was performed to characterize the crystal structures of these highly hole-doped nickelates. For the sample with , the Ni-O bond lengths decrease uniformly with decreasing temperature, and the atomic displacement parameters are similar to those for . In contrast, for the sample with , the out-of-plane Ni-O bond length shows a sharp thermal contraction in the high-temperature region, which is suggestive of changes in the orbital occupation accompanied by the development of checkerboard-type charge correlations. Furthermore, the sample is characterized by a large atomic displacement parameter for the apical O atoms along the out-of-plane direction, which is interpreted as the existence of two types of Ni $^{3+}$ sites with different orbital occupancies. The distinct difference between the sample and the lower-concentration compounds should be related to the development of checkerboard-type charge ordering in the metallic matrix and possible orbital ordering at the Ni $^{3+}$ sites at in the hole-doped layered nickel oxides.

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

被引用回数：1 パーセンタイル：73.27(Physics, Condensed Matter)

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：54.14(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

被引用回数：1 パーセンタイル：60.52(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

被引用回数：0 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：86.6(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

被引用回数：2 パーセンタイル：75.88(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

被引用回数：0 パーセンタイル：100(Nanoscience & Nanotechnology)

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

被引用回数：0 パーセンタイル：100(Nanoscience & Nanotechnology)

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：5 パーセンタイル：33.27(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

被引用回数：2 パーセンタイル：9.58

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.