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池田 陽一*; 梅本 好日古*; 松村 大樹; 辻 卓也; 橋本 勇輝*; 北澤 崇文*; 藤田 全基*
Materials Transactions, 64(9), p.2254 - 2260, 2023/09
被引用回数:0 パーセンタイル:0.00(Materials Science, Multidisciplinary)Extended X-ray absorption fine structure (EXAFS) and neutron diffraction experiments were carried out to clarify the typical features of the local structure of a family of medium-entropy alloys (CrCoNi, MnCoNi, and FeCoNi). A simple random cluster model was constructed for analyzing EXAFS spectra, and static and dynamic components of the mean-square relative displacement (MSRD) were separately extracted. In our analysis, the static MSRD of the MnCoNi sample was slightly larger than those of the CrCoNi and FeCoNi samples, whereas the dynamic MSRDs of these samples were almost identical. Based on the complementary neutron diffraction data, we argued that the origin of the large static displacement in the MnCoNi alloy can be associated with a short-range structural transformation through long-term structural relaxation.
北澤 崇文; 池田 陽一*; 榊原 俊郎*; 松尾 晶*; 清水 悠晴*; 徳永 陽; 芳賀 芳範; 金道 浩一*; 南部 雄亮*; 池内 和彦*; et al.
Physical Review B, 108(8), p.085105_1 - 085105_7, 2023/08
We demonstrate field-induced single-ion magnetic anisotropy resulting from the multiorbital Kondo effect on diluted ytterbium alloy (LuYb
)Rh
Zn
. Single-ion anisotropic metamagnetic behavior is revealed in low-temperature regions where the local Fermi-liquid state is formed. Specific heat, low-field magnetic susceptibility, and resistivity indicate reproduction of the ground-state properties by the SU(
= 8) Kondo model with a relatively large
-
hybridization of
= 60.9 K. Dynamical susceptibility measurements on YbRh
Zn
support realizing multiorbital Kondo ground state in (Lu
Yb
)Rh
Zn
. The single-ion magnetic anisotropy becomes evident above
5 T, which is lower than the isotropic Kondo crossover field of 22.7 T, verifying blurred low-lying crystal field states through the multiorbital Kondo effect.
Chen, Y.*; 浅野 駿*; Wang, T.*; Xie, P.*; 北山 慎之介*; 石井 賢司*; 松村 大樹; 辻 卓也; 谷口 貴紀*; 藤田 全基*
JPS Conference Proceedings (Internet), 38, p.011050_1 - 011050_6, 2023/05
To investigate the variation of the electronic state of -type cuprate due to annealing, we performed Cu
-edge X-ray absorption fine structure measurements on Pr
CuO
(PCO) and Pr
La
CuO
(PLCO). The induced electrons due to annealing (
) in PCO and PLCO were approximately 2
, consistent with a model of electron doping to Mott insulator. Here,
and
represent the amount of excess oxygen from the stoichiometric composition in the as-sintered compound and that of oxygen loss due to annealing, respectively. Furthermore, the energy of the Einstein oscillator (
) for the Cu-O
bond was evaluated by extended X-ray absorption fine structure analysis. (O
denotes the in-plane oxygen.) We found a small annealing effect on
for both PCO and PLCO.
池内 和彦*; 脇本 秀一; 藤田 全基*; 福田 竜生; 梶本 亮一; 新井 正敏*
Physical Review B, 105(1), p.014508_1 - 014508_7, 2022/01
被引用回数:2 パーセンタイル:30.40(Materials Science, Multidisciplinary)Spin excitations of layered copper oxide show various characteristic features, depending on the carrier concentration. In this paper, we conducted inelastic neutron-scattering measurements on LaSr
CuO
(LSCO) with
= 0, 0.075, 0.18, and 0.30 and La
Sr
NiO
(LSNO) with 1/3 to clarify the origin of the intensity enhancement in the excitation spectrum of LSCO at the energy (
) of 16-19 meV [Phys. Rev. B
, 224404 (2015),
, 094416 (2016)]. We confirmed the presence of a peak structure in the
dependence of the local spin susceptibility
of superconducting (SC) LSCO with a peak energy of 16-19 meV where the spin excitations intersect optical phonon branches. A comparable peak structure is not observed in the insulating La
CuO
, LSNO, and heavily overdoped LSCO with
= 0.30. A dome-shaped
dependence of the integrated intensity around the peak energies is revealed for the SC phase by summarizing the present and previously reported results. Furthermore, our phonon calculation on LCO shows the existence of two optical branches at
19 meV that could stabilize stripe alignment of carriers due to out-of-plane vibrations of Cu or O of the CuO
planes. These results indicate the interplay among spin, charge, and lattice dynamics and suggest that the intensity enhancement is associated with their composite excitations.
浅野 駿*; 石井 賢司*; 松村 大樹; 辻 卓也; 工藤 康太*; 谷口 貴紀*; 齋藤 真*; 春原 稔樹*; 川股 隆行*; 小池 洋二*; et al.
Physical Review B, 104(21), p.214504_1 - 214504_7, 2021/12
被引用回数:1 パーセンタイル:7.22(Materials Science, Multidisciplinary)We performed Cu K-edge X-ray absorption fine-structure measurements on -type La
Eu
CuO
(LECO) and Nd
CuO
(NCO) to investigate the variation in the electronic state associated with the emergence of superconductivity due to annealing. The X-ray absorption near-edge structure spectra of as-sintered (AS) LECO are quite similar to those of AS NCO, indicating that the ground state of AS LECO is a Mott insulator. The electron density after annealing
was evaluated for both superconducting LECO and nonsuperconducting NCO and was found to be 0.40 and 0.05 electron per Cu atom, respectively. In LECO but not in NCO, extended X-ray absorption fine-structure analysis revealed a reduction in the strength of the Cu-O bond in the CuO
plane due to annealing, which is consistent with the screening effect on phonons in the metallic state. The origin of the difference in doping processes due to annealing is discussed in relation to the size of the charge-transfer gap.
Chen, Y.*; 佐藤 正寛*; Tang, Y.*; 塩見 雄毅*; 大柳 洸一*; 益田 隆嗣*; 南部 雄亮*; 藤田 全基*; 齊藤 英治
Nature Communications (Internet), 12, p.5199_1 - 5199_7, 2021/08
被引用回数:9 パーセンタイル:66.25(Multidisciplinary Sciences)A triplon refers to a fictitious particle that carries angular momentum corresponding to the elementary excitation in a broad class of quantum dimerized spin systems. Such systems without magnetic order have long been studied as a testing ground for quantum properties of spins. Although triplons have been found to play a central role in thermal and magnetic properties in dimerized magnets with singlet correlation, a spin angular momentum flow carried by triplons, a triplon current, has not been detected yet. Here we report spin Seebeck effects induced by a triplon current: triplon spin Seebeck effect, using a spin-Peierls system CuGeO
. The result shows that the heating-driven triplon transport induces spin current whose sign is positive, opposite to the spin-wave cases in magnets. The triplon spin Seebeck effect persists far below the spin-Peierls transition temperature, being consistent with a theoretical calculation for triplon spin Seebeck effects.
藤田 全基*; 池内 和彦*; 梶本 亮一; 中村 充孝
Journal of the Physical Society of Japan, 90(2), p.025001_1 - 025001_2, 2021/02
被引用回数:1 パーセンタイル:15.50(Physics, Multidisciplinary)In this short note, we report on the first inelastic neutron scattering (INS) study on high-energy magnetic excitations in SrIr
O
. We observed excitations between
80 meV and
180 meV. The peak position of the excitations is consistent with the dispersion of a single magnon determined by resonant inelastic X-ray scattering (RIXS) measurement. Thus, our results demonstrate the feasibility of INS for iridates, which has a large neutron absorption cross-section.
佐藤 研太朗*; 池内 和彦*; 梶本 亮一; 脇本 秀一; 新井 正敏*; 藤田 全基*
Journal of the Physical Society of Japan, 89(11), p.114703_1 - 114703_7, 2020/11
被引用回数:6 パーセンタイル:49.07(Physics, Multidisciplinary)To elucidate the spin dynamics of LaSr
CuO
, which couples with the charge degree of freedom, the spin excitations spanning the characteristic energy (
35-40 meV) are investigated for underdoped
= 0.10 and optimally doped (OP)
= 0.16 through inelastic neutron scattering measurements. Analysis based on a two-component picture of high-quality data clarified the possible coexistence of upright standing incommensurate (IC) excitations with gapless commensurate (C) excitations in the energy-momentum space. The IC component weakens the intensity toward
with increasing energy transfer (
), whereas the C component strengthens at high-
regions. The analysis results imply that the superposition of two components with a particular intensity balance forms an hourglass-shaped excitation in appearance. Furthermore, the temperature dependence of the intensity of each component exhibits different behaviors; the IC component disappears near the pseudo-gap temperature (
) upon warming, whereas the C component is robust against temperature. These results suggest the itinerant electron spin nature and the localized magnetism of the parent La
CuO
in IC and C excitations, respectively, similar to the spin excitations in the OP YBa
Cu
O
and HgBa
CuO
with higher superconducting-transition temperatures.
南部 雄亮*; Barker, J.*; 沖野 夕貴*; 吉川 貴史*; 塩見 雄毅*; Enderle, M.*; Weber, T.*; Winn, B.*; Graves-Brook, M.*; Tranquada, J. M.*; et al.
Physical Review Letters, 125(2), p.027201_1 - 027201_6, 2020/07
被引用回数:47 パーセンタイル:94.38(Physics, Multidisciplinary)We measure the mode-resolved direction of the precessional motion of the magnetic order, i.e., magnon polarization, via the chiral term of inelastic polarized neutron scattering spectra. The magnon polarization is a unique and unambiguous signature of magnets and is important in spintronics, affecting thermodynamic properties such as the magnitude and sign of the spin Seebeck effect. However, it has never been directly measured in any material until this work. The observation of both signs of magnon polarization in YFe
O
also gives direct proof of its ferrimagnetic nature. The experiments agree very well with atomistic simulations of the scattering cross section.
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
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)A high-resolution time-of-flight powder neutron diffraction study of the layered nickel oxide PrSr
NiO
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
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
sites at
in the hole-doped layered nickel oxides.
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
被引用回数:0 パーセンタイル:0.00(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、LaSr
Cu
Al
O
の巨大単結晶について、磁気励起を測定した。
浅野 駿*; 石井 賢司*; 松村 大樹; 辻 卓也; 伊奈 稔哲*; 鈴木 謙介*; 藤田 全基*
Journal of the Physical Society of Japan, 87(9), p.094710_1 - 094710_5, 2018/09
被引用回数:13 パーセンタイル:66.22(Physics, Multidisciplinary)We investigated the Ce substitution and reduction annealing effects on the electronic states at copper sites by Cu -edge X-ray absorption near-edge structure measurements in Pr
Ce
CuO
(PCCO) with varying
and
(amount of oxygen loss during annealing). Absorption near-edge spectra were modified by Ce substitution and reduction annealing similarly with increasing
and
. Considering electron doping by Ce substitution, this similarity indicates an increase in electron number at the copper sites due to annealing (
). Furthermore, quantitative analyses of the spectra clarified that the number of Cu
sites, corresponding to the induced electron number by Ce substitution increases linearly with
in the as-sintered PCCO, whereas
is not exactly equal to 2
. For each
-fixed sample,
tends to exceed 2
with increasing
, suggesting the emergence of two types of carrier due to annealing.
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
被引用回数:6 パーセンタイル:93.67(Physics, Applied)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.
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
被引用回数:2 パーセンタイル:10.13(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、LaSr
CuO
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
= (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、
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
Sr
CuO
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。
浅野 駿*; 鈴木 謙介*; 松村 大樹; 石井 賢司*; 伊奈 稔哲*; 藤田 全基*
Journal of Physics; Conference Series, 969, p.012051_1 - 012051_5, 2018/04
被引用回数:3 パーセンタイル:81.69(Physics, Applied)Reduction and oxidation annealing effects on the electronic states around the copper sites for PrCe
CuO
and Nd
Ce
CuO
with
= 0 and
= 0.15 were investigated by Cu
-edge X-ray absorption measurements. Cu
near-edge spectra were changed by the reduction annealing in a manner similar to the case of Ce substitution for both
= 0 and
= 0.15. This means an increase of electron density at the copper sites, indicating the aspect of electron doping in the reduction annealing. This reduction annealing effect on the near-edge spectra are reverted by the additional oxidation annealing. The amount of electron density around the copper sites is varied by the reduction and oxidation annealing, reversibly, corresponding to the reversible variation of the physical property from insulating to superconductivity.
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
被引用回数:1 パーセンタイル:52.34(Physics, Applied)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 LaSr
Cu
Fe
O
. 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.
中島 健次; 川北 至信; 伊藤 晋一*; 阿部 淳*; 相澤 一也; 青木 裕之; 遠藤 仁*; 藤田 全基*; 舟越 賢一*; Gong, W.*; et al.
Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12
J-PARC物質・生命科学実験施設の中性子実験装置についてのレビューである。物質・生命科学実験施設には23の中性子ビームポートがあり21台の装置が設置されている。それらは、J-PARCの高性能な中性子源と最新の技術を組み合わせた世界屈指の実験装置群である。このレビューでは、装置性能や典型的な成果等について概観する。
石井 賢司*; 遠山 貴巳*; 浅野 駿*; 佐藤 研太朗*; 藤田 全基*; 脇本 秀一; 筒井 健二*; 曽田 繁利*; 宮脇 淳*; 丹羽 秀治*; et al.
Physical Review B, 96(11), p.115148_1 - 115148_8, 2017/09
被引用回数:29 パーセンタイル:77.38(Materials Science, Multidisciplinary)We investigate electronic excitations in La(Br,Sr)
CuO
using resonant inelastic X-ray scattering (RIXS) at the oxygen
edge. We observed momentum-dependent spectral weight below 1 eV, which is consistent with theoretical calculation of the dynamical charge structure factor on oxygen orbitals in a three-band Hubbard model. Our results confirm that the momentum-dependent charge excitations exist on the order of the transfer energy (
), and the broad spectral line shape indicates damped and incoherent character of the charge excitations at the energy range in the doped Mott insulators.
松浦 直人*; 川村 奨*; 藤田 全基*; 梶本 亮一; 山田 和芳*
Physical Review B, 95(2), p.024504_1 - 024504_6, 2017/01
被引用回数:10 パーセンタイル:45.30(Materials Science, Multidisciplinary)Inelastic neutron scattering measurements of magnetic excitations in hole-doped high- cuprates La
Sr
CuO
(
and 0.075) have been performed over a wide temperature range of 5
500 K extending beyond the pseudogap temperature of
360 K for
. For
, the two-dimensional spin-wave excitations at low temperatures are thermally robust and the dispersion is slightly softened on heating up to
K. For
, the spin-wave-like excitations in the upper part of the hourglass-shaped dispersion remain at
K. However, further heating above
K induces a broad ridge centered at
; thereby the hourglass-shaped dispersion becomes blurred above the pseudogap temperature. The localized spin nature of magnetic excitations below
suggests that the pseudogap is related to a proximity to a Mott insulator rather than being a precursor of Cooper pairs.
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.