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Fine, L.*; Lavn, R.*; Wei, Z.*; 津森 竜也*; 陰山 洋*; 梶本 亮一; Jimen
z-Ruiz, M.*; Koza, M. M.*; Karlsson, M.*
Chemistry of Materials, 37(1), p.489 - 496, 2024/12
被引用回数:0 パーセンタイル:0.00(Chemistry, Physical)We report results on the configuration and vibrational dynamics of hydride-ions (H) in the novel nitridehydride catalyst Ca
CrN
H, by means of variable temperature inelastic neutron scattering (INS) experiments, harmonic phonon calculations, and machine-learning molecular dynamics (MLMD) calculations. The combined analyses of experimental and theoretical data show that the vibrational dynamics of H
are manifested as a broad, asymmetric vibrational band between 80 and 130 meV. Crucially, these modes are polarized along the crystallographic
axis, and their dispersive character reveals significant interactions between neighbouring H
in the material. We find that most H
are surrounded by two other H
and that the H
sites of the studied sample have an occupancy of at least 95%. We argue that this high H
occupancy may be related to the material's high efficiency as a catalyst for ammonia synthesis.
木村 耕治*; 筒井 智嗣*; 山本 裕太*; 中埜 彰俊*; 川村 啓介*; 梶本 亮一; 蒲沢 和也*; Martin, A.*; Webber, K. G.*; 柿本 健一*; et al.
Physical Review B, 110(13), p.134314_1 - 134314_10, 2024/10
被引用回数:0 パーセンタイル:0.00(Materials Science, Multidisciplinary)We performed inelastic X-ray and neutron scattering (IXS and INS) experiments for (Ba,Ca)TiO single crystals to elucidate the effect of Ca doing on the atomic dynamics. Dispersion relations of transverse phonons in BaTiO
, (Ba
Ca
)TiO
, and (Ba
Ca
)TiO
were determined. The
-site-O vibrational mode as well as the acoustic mode were observed both by IXS and INS, whereas the Ti-O soft mode was detected only by INS. It was found that the
-site-O vibration exhibits significant softening with increasing Ca concentration, while the Ti-O soft mode is almost unaffected by the Ca doping. This finding is discussed in comparison with the polarization hysteresis loops and piezoelectric coefficients of (Ba,Ca)TiO
. It is indicated that the softening of the
-site-O vibration contributes to the enhancement of the piezoelectricity of Ca-doped BaTiO
-based materials.
Liao, J.*; Huang, Z.*; Shangguan, Y.*; Zhang, B.*; Cheng, S.*; Xu, H.*; 梶本 亮一; 蒲沢 和也*; Bao, S.*; Wen, J.*
Physical Review B, 109(22), p.224411_1 - 224411_10, 2024/06
被引用回数:0 パーセンタイル:0.00(Materials Science, Multidisciplinary)Antiferromagnetic van der Waals family P
(
= Fe, Mn, Co, and Ni;
= S and Se) have attracted significant research attention due to the possibility of realizing long-range magnetic order down to the monolayer limit. Here, we perform inelastic neutron scattering measurements on single-crystal samples of MnPSe
, a member of the
P
family, to study the spin dynamics and determine the effective spin model. The excited magnon bands are well characterized by a spin model, which includes a Heisenberg term with three intraplane exchange parameters (
meV,
meV,
meV) and one interplane parameter (
meV), and an easy-plane single-ion anisotropy term (
meV). Additionally, we observe the intersection of the magnon and phonon bands but no anomalous spectral features induced by the formation of magnon-phonon hybrid excitations at the intersecting region. We discuss possible reasons for the absence of such hybrid excitations in MnPSe
.
Park, P.*; Cho, W.*; Kim, C.*; An, Y.*; Avdeev, M.*; 飯田 一樹*; 梶本 亮一; Park, J.-G.*
Physical Review B, 109(6), p.L060403_1 - L060403_7, 2024/02
被引用回数:3 パーセンタイル:85.41(Materials Science, Multidisciplinary)Spontaneous Hall conductivity has recently been reported in the triangular lattice antiferromagnet CoTaS
under a zero magnetic field. This phenomenon originates from the distinctive noncoplanar triple-
magnetic ground state, possessing uniform real-space Berry curvature characterized by scalar spin chirality. We investigated the physical properties of Co
TaS
by judiciously controlling the composition, revealing a drastic change in its bulk properties, even by slight variations in cobalt composition, despite the same crystal structure. For
, Co
TaS
keeps all the characteristics of the ground state consistent with the previous studies - two antiferromagnetic phase transitions at
and
(
), a large spontaneous Hall conductivity [
], and a weak ferromagnetic moment along the
axis. However, samples with
exhibit distinct bulk properties, including the absence of both
and the weak ferromagnetic moment. Our neutron diffraction data reveal that Co
TaS
with
develops coplanar helical magnetic order with
. This is entirely different from what has been seen in
, explaining the observed composition dependence.
Huang, Z.*; Wang, W.*; Ye, H.*; Bao, S.*; Shangguan, Y.*; Liao, J.*; Cao, S.*; 梶本 亮一; 池内 和彦*; Deng, G.*; et al.
Physical Review B, 109(1), p.014434_1 - 014434_9, 2024/01
被引用回数:0 パーセンタイル:0.00(Materials Science, Multidisciplinary)TbMnSn
is a correlated topological magnet with a Mn-based kagome lattice, in which a Chern gap opens at the Dirac point at low temperatures. The magnetic moment direction of the ferrimagnetic order changes from in the kagome plane to the out-of-plane upon cooling, which is essential for generating the Chern gap, but the underlying mechanism for the spin reorientation remains elusive. Here, we investigate the spin-reorientation transition in TbMn
Sn
using neutron scattering. We provide direct evidence for the spin-reorientation transition and unveil the coexistence of two Tb modes at 200 K. To account for these results, we put forward a model based on SU(N) spin-wave theory, in which there is a temperature evolution of the ground state Tb
orbitals, driven by the crystalline electric field, single-ion anisotropy, and exchange interactions between Tb and Mn ions. Our findings shed light on the complex magnetism of TbMn
Sn
, despite its relatively simple ground state magnetic structure, and provide insights into the mechanisms for tuning magnetic topological materials.
Park, P.*; Cho, W.*; Kim, C.*; An, Y.*; Kang, Y.-G.*; Avdeev, M.*; Sibille, R.*; 飯田 一樹*; 梶本 亮一; Lee, K. H.*; et al.
Nature Communications (Internet), 14, p.8346_1 - 8346_9, 2023/12
被引用回数:13 パーセンタイル:81.42(Multidisciplinary Sciences)The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120 structure. However, a new triple-
chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals. We report the metallic TLAF Co
TaS
as the first example of tetrahedral triple-
magnetic ordering with the associated topological Hall effect (non-zero
). We also present a theoretical framework that describes the emergence of this magnetic ground state, which is further supported by the electronic structure measured by angle-resolved photoemission spectroscopy. Additionally, our measurements of the inelastic neutron scattering cross section are consistent with the calculated dynamical structure factor of the tetrahedral triple-
state.
Bao, S.*; Gu, Z.-L.*; Shangguan, Y.*; Huang, Z.*; Liao, J.*; Zhao, X.*; Zhang, B.*; Dong, Z.-Y.*; Wang, W.*; 梶本 亮一; et al.
Nature Communications (Internet), 14, p.6093_1 - 6093_9, 2023/09
被引用回数:14 パーセンタイル:92.03(Multidisciplinary Sciences)Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic FeMo
O
possessing strong magnon-phonon coupling. Specifically, below the magnetic ordering temperature, a gap opens at the nominal intersection of the original magnon and phonon bands, leading to two separated magnon-polaron bands. Each of the bands undergoes mixing, interconverting and reversing between its magnonic and phononic components. We attribute the formation of magnon polarons to the strong magnon-phonon coupling induced by Dzyaloshinskii-Moriya interaction. Intriguingly, we find that the band-inverted magnon polarons are topologically nontrivial. These results uncover exotic elementary excitations arising from the magnon-phonon coupling, and offer a new route to topological states by considering hybridizations between different types of fundamental excitations.
高濱 隆成*; 有薗 実駿*; 犬童 代梧*; 吉永 汰正*; 寺倉 千恵子*; 竹下 直*; 白崎 巧*; 野田 正亮*; 桑原 英樹*; 梶本 亮一; et al.
JPS Conference Proceedings (Internet), 38, p.011114_1 - 011114_6, 2023/05
We investigated the transport and magnetic properties of single crystals of the pseudobrookite AlTi
O
for
grown using a floating zone. We found a correlation of spin-singlet Ti
-Ti
dimers even in the conductive
and
phases which develops with increasing
. The development of the dimer correlation suppresses the magnetic susceptibility at the low temperature and enhances the electric conductivity perhaps due to the suppression of the magnetic scattering at the isolated Ti
ions. The compound shows the best conductivity in the
phase near the phase boundary between the
and
phases where the dimer correlation is much developed. Some exotic conductive state may be realized under the background of fluctuation of the spin-singlet dimer in the
phase near the phase boudary.
佐藤 節夫*; 梶本 亮一; 稲村 泰弘
Journal of Neutron Research, 24(3-4), p.427 - 434, 2023/01
In many neutron scattering experiments, He-gas position-sensitive detectors (PSDs) are employed to obtain high-quality data. However, the exact position where a neutron is detected cannot be determined if two or more neutrons are simultaneously captured at different positions. This results in noise and degrades the quality of the data. In particular, such noise is a serious source of spurious scattering in inelastic neutron scattering instruments equipped with a large number of long PSDs recently developed at pulsed neutron sources. Herein, we introduce a pulse-width-discriminating PSD system that monitors the pulse width and height of the collected data. The system utilizes previously developed neutron-readout boards and removes instances of two or more simultaneous captures from the data to significantly improve the performance of PSDs. We also propose a new program to monitor the pulse width from PSD data using a hardware function implemented for other purposes. We confirm that the noise decreases to a level almost equal to that of the background. Although the developed program is applied to an inelastic scattering experiment, it is applicable to other types of experiments in which mispositioned signals should be eliminated as noise.
Wu, P.*; 村井 直樹; Li, T.*; 梶本 亮一; 中村 充孝; 古府 麻衣子; 中島 健次; Xia, K.*; Peng, K.*; Zhang, Y.*; et al.
New Journal of Physics (Internet), 25(1), p.013032_1 - 013032_11, 2023/01
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)The understanding of the lattice dynamics is essential for engineering the thermal transport properties in quantum materials. Based on the canonical point of view, acoustic phonons are believed to be the principal thermal carriers in heat flow. Here, in this work, optical phonons are elucidated to play a pivotal role in determining the lattice thermal conductivity in thermoelectric material SnS by using the state-of-the-art inelastic neutron scattering technique combined with first-principles calculations. Additionally, in contrast to acoustic phonons, optical phonons are observed to exhibit pronounced softening and broadening with temperature. Our observations not only shed light on the significance of the optical phonons in thermal transport but also provide a vital clue to suppress the propagation of optical phonons to optimize the thermoelectric performance of SnS.
梶本 亮一; 中村 充孝; 蒲沢 和也*; 稲村 泰弘; 飯田 一樹*; 池内 和彦*; 石角 元志*
EPJ Web of Conferences, 272, p.02007_1 - 02007_8, 2022/11
4SEASONS is a direct geometry time-of-flight spectrometer installed in the Materials and Life Science Experimental Facility, the Japan Proton Accelerator Research Complex. It is used to study atomic andspin dynamics in the energy range of meV to
meV. Since more than a decade has crossed after the first inelastic scattering experiment, it is essential to consider upgrading the instrument to improve its flexibility and performance. In this paper, we discuss the possible medium-term upgrades of key components of the instrument like the chopper system, which are achievable with the current technology and at reasonable cost. Herein, we demonstrated that 4SEASONS can improve the energy resolution by a factor of two, remove frame overlap of adjacent incident energies, significantly improve the asymmetry in the pulse shape, and increase the flux by a factor of
1.5, without major technical difficulties.
Xie, T.*; Liu, C.*; 梶本 亮一; 池内 和彦*; Li, S.*; Luo, H.*
Journal of Physics; Condensed Matter, 34(47), p.474001_1 - 474001_8, 2022/11
被引用回数:0 パーセンタイル:0.00(Physics, Condensed Matter)We report time-of-flight inelastic neutron scattering (INS) investigations on the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC) CaLa
Fe
Ni
As
(CaLa-112). In comparison to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure (space group
) at room temperature and an in-plane stripe-type antiferromagnetic (AF) order at low temperature, the 112 system has a noncentrosymmetric structure (space group
) with additional zigzag arsenic chains between Ca/La layers and a magnetic ground state with similar wavevector
but different orientations of ordered moments in the parent compounds. Our INS study clearly reveals that the in-plane dispersions and the bandwidth of spin excitations in the superconducting CaLa-112 closely resemble to those in 122 systems. While the total fluctuating moments
/Fe are larger than 122 system, the dynamic correlation lengths are similar (
). These results suggest that superconductivity in iron arsenides may have a common magnetic origin under similar magnetic exchange couplings with a dual nature from local moments and itinerant electrons, despite their different magnetic patterns and lattice symmetries.
Yu, Y.*; Yang, C.*; Baggioli, M.*; Phillips, A. E.*; Zaccone, A.*; Zhang, L.*; 梶本 亮一; 中村 充孝; Yu, D.*; Hong, L.*
Nature Communications (Internet), 13, p.3649_1 - 3649_10, 2022/06
被引用回数:20 パーセンタイル:90.31(Multidisciplinary Sciences)The vibrational properties of crystalline bulk materials are well described by Debye theory, which successfully predicts the quadratic low-frequency scaling of the vibrational density of states. However, the analogous framework for nanoconfined materials with fewer degrees of freedom has been far less well explored. Using inelastic neutron scattering, we characterize the vibrational density of states of amorphous ice confined inside graphene oxide membranes and we observe a crossover from the Debye
scaling to an anomalous
behaviour upon reducing the confinement size L.
Do, S.-H.*; 金子 耕士; 梶本 亮一; 蒲沢 和也*; Stone, M. B.*; Lin, J. Y. Y.*; 伊藤 晋一*; 益田 隆嗣*; Samolyuk, G. D.*; Dagotto, E.*; et al.
Physical Review B, 105(18), p.L180403_1 - L180403_6, 2022/05
被引用回数:20 パーセンタイル:87.69(Materials Science, Multidisciplinary)We report inelastic neutron scattering studies of the prototypical kagome magnetic metal FeSn. The spectra display well defined spin waves extending up to 120 meV. Above this energy, the spin waves become progressively broadened, reflecting interactions with the Stoner continuum. Using linear spin wave theory, we determine an effective spin Hamiltonian that explains the measured dispersion. This analysis indicates that the Dirac magnon at the K point occurs on the brink of a region where well defined spin waves become unobservable. Our results emphasize the influential role of itinerant carriers on the topological spin excitations of metallic kagome magnets.
齋藤 睦己*; 高岸 龍之介*; 栗田 伸之*; 渡邊 正理*; 田中 秀数*; 野村 竜司*; 福元 好志*; 池内 和彦*; 梶本 亮一
Physical Review B, 105(6), p.064424_1 - 064424_15, 2022/02
被引用回数:7 パーセンタイル:60.50(Materials Science, Multidisciplinary)CsCu
SnF
is a spin-
antiferromagnet on a nearly uniform kagome lattice. This compound undergoes magnetic ordering with the
= 0 structure and positive chirality, which is mainly caused by the large Dzyaloshinskii-Moriya interaction. Rb
Cu
SnF
is a spin-
antiferromagnet on a modified kagome lattice with a
enlarged chemical unit cell at room temperature. Its ground state is a pinwheel valence bond solid (VBS) with an excitation gap. Here, we show the structures of magnetic excitations in Cs
Cu
SnF
and Rb
Cu
SnF
investigated by inelastic neutron scattering in wide energy and momentum ranges. For Cs
Cu
SnF
, four single-magnon excitation modes were observed. It was confirmed that the energy of single-magnon excitations arising from the
point in the extended Brillouin zones is largely renormalized downwards. It was found that the broad excitation continuum without a marked structure spreads in a wide energy range from
to approximately
. These findings strongly suggest spinon excitations as elementary excitations in Cs
Cu
SnF
. In Rb
Cu
SnF
, singlet-triplet excitations from the pinwheel VBS state and their ghost modes caused by the enlargement of the chemical unit cell were clearly confirmed. It was found that the excitation continuum is structured in the low-energy region approximately below
and the almost structureless high-energy excitation continuum extends to approximately
. The characteristics of the high-energy excitation continuum are common to both Cs
Cu
SnF
and Rb
Cu
SnF
, irrespective of their ground states. The experimental results strongly suggest that the spin liquid component remains in the ground state as quantum fluctuations in Cs
Cu
SnF
and Rb
Cu
SnF
.
Bao, S.*; Wang, W.*; Shangguan, Y.*; Cai, Z.*; Dong, Z.-Y.*; Huang, Z.*; Si, W.*; Ma, Z.*; 梶本 亮一; 池内 和彦*; et al.
Physical Review X, 12(1), p.011022_1 - 011022_15, 2022/02
被引用回数:29 パーセンタイル:94.47(Physics, Multidisciplinary)In the local or itinerant extreme, magnetic excitations can be described by the Heisenberg model which treats electron spins as localized moments, or by the itinerant-electron model where the exchange interaction between electrons leads to unequal numbers of electrons with up and down spins. However, the nature of the magnetic excitations has been elusive when both local moments and itinerant electrons are present in the intermediate range. Using inelastic neutron scattering, we provide direct spectroscopic evidence on the coexistence of and interplay between local moments and itinerant electrons in a van der Waals metallic ferromagnet FeGeTe
, which can sustain tunable room-temperature ferromagnetism down to the monolayer limit. We find that there exist ferromagnetic spin-wave excitations dispersing from the zone center at low energies resulting from local moments and a columnlike broad continuum at the zone boundary at high energies up to over 100 meV resulting from itinerant electrons. Unlike the two-dimensional crystal structure, the low-energy mode exhibits a three-dimensional nature, and the high-energy mode also has an out-of-plane dependence. Both modes persist well above the Curie temperature of 160 K. Our neutron spectroscopic data reveal that the low-energy spin waves at 100 K are more coherent than those at 4 K, which is evidence of the weakening of the Kondo screening at high temperatures. These results unambiguously demonstrate the coexistence of local moments and itinerant electrons and the Kondo effect between these two components in Fe
GeTe
. Such behaviors are generally expected in heavy-fermion systems with heavy
electrons but are rarely clearly observed in materials with light
electrons. These findings shed light on the understanding of magnetism in transition-metal compounds.
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:3 パーセンタイル:30.22(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.
Shangguan, Y.*; Bao, S.*; Dong, Z.-Y.*; Cai, Z.*; Wang, W.*; Huang, Z.*; Ma, Z.*; Liao, J.*; Zhao, X.*; 梶本 亮一; et al.
Physical Review B, 104(22), p.224430_1 - 224430_8, 2021/12
被引用回数:2 パーセンタイル:12.24(Materials Science, Multidisciplinary)Dimerized magnets forming alternating Heisenberg chains exhibit quantum coherence and entanglement and thus can find potential applications in quantum information and computation. However, magnetic systems typically undergo thermal decoherence at finite temperatures. Here, we show inelastic neutron scattering results on an alternating antiferromagnetic-ferromagnetic chain compound NaCu
TeO
that the excited quasiparticles can counter thermal decoherence and maintain strong correlations at elevated temperatures. At low temperatures, we observe clear dispersive singlet-triplet excitations arising from the dimers formed along the crystalline
-axis. The excitation gap is of
18 meV and the bandwidth is about half of the gap. The band top energy has a weak modulation along the [100] direction, indicative of a small interchain coupling. The gap increases while the bandwidth decreases with increasing temperature, leading to a strong reduction in the available phase space for the triplons. As a result, the Lorentzian-type energy broadening becomes highly asymmetric as the temperature is raised. These results are associated with a strongly correlated state resulting from hard-core constraint and quasiparticle interactions. We consider these results to be not only evidence for strong correlations at finite temperatures in Na
Cu
TeO
, but also for the universality of the strongly correlated state in a broad range of quantum magnetic systems.
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:12.77(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.
社本 真一; 山内 宏樹; 池内 和彦*; 梶本 亮一; 家田 淳一
Physical Review Research (Internet), 3(1), p.013169_1 - 013169_9, 2021/02
A compound with large anions is known to show large compressibility whereby a novel response may emerge from the degenerated state by a uniaxial pressure. Neutron scattering study of BaCoNi
S
crystal reveals that the tetragonal insulating state has two magnetic domains with in-plane anisotropic antiferromagnetic wave vectors
=(
, 0) and
=(0,
). One magnetic domain with
becomes dominant under a weak uniaxial pressure of 1 MPa without a structural phase transition. Correspondingly, the in-plane broken C
symmetry is observed in the in-plane magnetic excitation. The domain-ratio changes under a uniaxial pressure in the tetragonal state is only slightly smaller than that in the orthorhombic state.