Magnetic excitations in the noncentrosymmetric magnet SrMnSiO

Kawamata, Masahiro*; Pang, X.*; Murakawa, Hiroshi*; Kawamura, Seiko; Nakajima, Kenji; Masuda, Hidetoshi*; Fujita, Masaki*; Hanasaki, Noriaki*; Onose, Yoshinori*; Nambu, Yusuke*

Physical Review Materials (Internet), 9(1), p.014407_1 - 014407_6, 2025/01

https://doi.org/10.1103/PhysRevMaterials.9.014407

Nanometer-thick crystalline ice plates in rapidly-frozen glucose solution observed by spin-contrast-variation small-angle neutron scattering

Kumada, Takayuki; Nakagawa, Hiroshi; Miura, Daisuke; Sekine, Yurina; Motokawa, Ryuhei; Hiroi, Kosuke; Inamura, Yasuhiro; Oku, Takayuki; Oishi, Kazuki*; Morikawa, Toshiaki*; et al.

Hamon, 34(2), p.50 - 53, 2024/05

Spin-contrast-variation (SCV) small-angle neutron scattering (SANS) enabled us to determine structure of nano-ice crystals that were generated in rapidly frozen sugar solution. In the frozen glucose solution, we found that the nano-ice crystals formed a planar structure with a radius larger than several tens of nanometers and a thickness of 2-3 nm, which was close to the critical nucleation size of ice crystals in supercooled water. This result suggests that the glucose molecules were preferentially bound to a specific face of nano-ice crystals, and then blocked the crystal growth perpendicular to that face.

Magnetic boson peak in classical spin glasses

Kofu, Maiko; Kawamura, Seiko; Murai, Naoki; Ishii, Rieko*; Hirai, Daigoro*; Arima, Hiroshi*; Funakoshi, Kenichi*

Physical Review Research (Internet), 6(1), p.013006_1 - 013006_9, 2024/01

https://doi.org/10.1103/PhysRevResearch.6.013006

Present status of J-PARC MUSE

Shimomura, Koichiro*; Koda, Akihiro*; Pant, A. D.*; Natori, Hiroaki*; Fujimori, Hiroshi*; Umegaki, Izumi*; Nakamura, Jumpei*; Tampo, Motonobu*; Kawamura, Naritoshi*; Teshima, Natsuki*; et al.

Journal of Physics; Conference Series, 2462, p.012033_1 - 012033_5, 2023/03

https://doi.org/10.1088/1742-6596/2462/1/012033

Effect of different interlayer counter-ions on montmorillonite swelling; Key controlling factors evaluated by molecular dynamic simulations

Yotsuji, Kenji*; Tachi, Yukio; Sakuma, Hiroshi*; Kawamura, Katsuyuki*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 29(2), p.63 - 81, 2022/12

https://doi.org/10.3327/jnuce.29.2_63

The understanding of the swelling phenomenon of montmorillonite is essential to predict the physical and chemical behavior of clay-based barriers in radioactive waste disposal systems. This study investigated the key factors controlling crystalline swelling behavior of montmorillonite with different interlayer counter-ions by molecular dynamics (MD) simulations. On the basis of the comparisons between MD simulated and experimental results, the water content in the interlayer in five homoionic (Na, K, Cs, Ca and Sr) montmorillonite was strongly correlated to the hydration number and the preference of an outer- or inner-sphere complex of each counter-ion. The detailed analysis for these results offer insights that the hydration number is controlled by the hydration free energy, the volume and the distribution of each interlayer counter-ion. The systematic MD simulations with virtually variable parameters clarified that the hydration free energy and the charge of interlayer counter- ions compete as influencing factors, and the control the formation rate of an outer-sphere complex of each counter-ion. The empirical relationships between these key factors will allow essential insights into predicting the swelling behavior of montmorillonite with different interlayer counter-ions.

Development of spin-contrast-variation neutron powder diffractometry for extracting the structure factor of hydrogen atoms

Miura, Daisuke*; Kumada, Takayuki; Sekine, Yurina; Motokawa, Ryuhei; Nakagawa, Hiroshi; Oba, Yojiro; Ohara, Takashi; Takata, Shinichi; Hiroi, Kosuke; Morikawa, Toshiaki*; et al.

Journal of Applied Crystallography, 54(2), p.454 - 460, 2021/04

AA2020-0724.pdf:2.05MB

https://doi.org/10.1107/S1600576721000303

We developed a spin-contrast-variation neutron powder diffractometry technique that extracts the structure factor of hydrogen atoms, namely, the contribution of hydrogen atoms to a crystal structure factor. Crystals of L-glutamic acid were dispersed in a dpolystyrene matrix containing 4-methacryloyloxy-2,2,6,6,-tetramethyl-1-piperidinyloxy (TEMPO methacrylate) to polarize their proton spins dynamically. The intensities of the diffraction peaks of the sample changed according to the proton polarization, and the structure factor of the hydrogen atoms was extracted from the proton-polarization dependent intensities. This technique is expected to enable analyses of the structures of hydrogen-containing materials that are difficult to determine with conventional powder diffractometry.

Emergent spin-1 Haldane gap and ferroelectricity in a frustrated spin- ladder

Ueda, Hiroshi*; Onoda, Shigeki*; Yamaguchi, Yasuhiro*; Kimura, Tsuyoshi*; Yoshizawa, Daichi*; Morioka, Toshiaki*; Hagiwara, Masayuki*; Hagihara, Masato*; Soda, Minoru*; Masuda, Takatsugu*; et al.

Physical Review B, 101(14), p.140408_1 - 140408_6, 2020/04

https://doi.org/10.1103/PhysRevB.101.140408

A New approach for measuring the muon anomalous magnetic moment and electric dipole moment

Abe, Mitsushi*; Bae, S.*; Beer, G.*; Bunce, G.*; Choi, H.*; Choi, S.*; Chung, M.*; da Silva, W.*; Eidelman, S.*; Finger, M.*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(5), p.053C02_1 - 053C02_22, 2019/05

https://doi.org/10.1093/ptep/ptz030

This paper introduces a new approach to measure the muon magnetic moment anomaly and the muon electric dipole moment (EDM) at the J-PARC muon facility. The goal of our experiment is to measure and using an independent method with a factor of 10 lower muon momentum, and a factor of 20 smaller diameter storage-ring solenoid compared with previous and ongoing muon g-2 experiments with unprecedented quality of the storage magnetic field. Additional significant differences from the present experimental method include a factor of 1000 smaller transverse emittance of the muon beam (reaccelerated thermal muon beam), its efficient vertical injection into the solenoid, and tracking each decay positron from muon decay to obtain its momentum vector. The precision goal for is a statistical uncertainty of 450 parts per billion (ppb), similar to the present experimental uncertainty, and a systematic uncertainty less than 70 ppb. The goal for EDM is a sensitivity of ecm.

Molecular dynamics simulations of physical properties of water and cations in montmorillonite interlayer; Application to diffusion model

Yotsuji, Kenji*; Tachi, Yukio; Kawamura, Katsuyuki*; Arima, Tatsumi*; Sakuma, Hiroshi*

Nendo Kagaku, 58(1), p.8 - 25, 2019/00

https://doi.org/10.11362/jcssjnendokagaku.58.1_8

Molecular dynamics (MD) simulations were conducted to investigate physical properties of water and cations in montmorillonite interlayer nanopores. The swelling behaviors and hydration states were firstly evaluated as functions of interlayer cations and layer charge. The diffusion coefficients of water and cations in interlayer nanopores were decreased in comparison with those in bulk water and came closer to those in bulk water when basal spacing increased. The viscosity coefficients of interlayer water estimated indicated a significant effect of viscoelectricity at 1- and 2-layer hydration states and higher layer charge of montmorillonite. These trends from MD calculations were confirmed to be consistent with existing measured data and previous MD simulation. In addition, model and parameter related to viscoelectric effect used in the diffusion model was refined based on comparative discussion between MD simulations and measurements. The series of MD calculations could provide atomic level understanding for the developments and improvements of the diffusion model for compacted montmorillonite.

Continuum excitation and pseudospin wave in quantum spin-liquid and quadrupole ordered states of TbTiO

Kadowaki, Hiroaki*; Wakita, Mika*; Fk, B.*; Ollivier, J.*; Kawamura, Seiko; Nakajima, Kenji; Takatsu, Hiroshi*; Tamai, Mototake*

Journal of the Physical Society of Japan, 87(6), p.064704_1 - 064704_6, 2018/06

https://doi.org/10.7566/JPSJ.87.064704

The ground states of the frustrated pyrochlore oxide TbTiO have been studied by inelastic neutron scattering experiments. Three single-crystal samples are investigated; one shows no phase transition (), being a putative quantum spin-liquid (QSL), and the other two () show electric quadrupole ordering (QO) below K. The QSL sample shows continuum excitation spectra with an energy scale 0.1 meV as well as energy-resolution-limited (nominally) elastic scattering. As is increased, pseudospin wave of the QO state emerges from this continuum excitation, which agrees with that of powder samples and consequently verifies good control for the present single crystal samples.