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Nirei, Masami; Kofu, Maiko; Nakajima, Kenji; Kikuchi, Tatsuya*; Kawamura, Seiko; Murai, Naoki; Harada, Masahide; Inamura, Yasuhiro
Journal of Neutron Research, 26(2-3), p.75 - 82, 2024/09
Zhu, L.*; He, H.*; Naeem, M.*; Sun, X.*; Qi, J.*; Liu, P.*; Harjo, S.; Nakajima, Kenji; Li, B.*; Wang, X.-L.*
Physical Review Letters, 133(12), p.126701_1 - 126701_6, 2024/09
Zeng, Z.*; Zhou, C.*; Zhou, H.*; Han, L.*; Chi, R.*; Li, K.*; Kofu, Maiko; Nakajima, Kenji; Wei, Y.*; Zhang, W.*; et al.
Nature Physics, 20(7), p.1097 - 1102, 2024/07
Times Cited Count:3 Percentile:93.28(Physics, Multidisciplinary)Li, J.*; Li, X.*; Zhang, Y.*; Zhu, J.*; Zhao, E.*; Kofu, Maiko; Nakajima, Kenji; Avdeev, M.*; Liu, P.-F.*; Sui, J.*; et al.
Applied Physics Reviews (Internet), 11(1), p.011406_1 - 011406_8, 2024/03
Times Cited Count:6 Percentile:97.19(Physics, Applied)Ren, Q.*; Gupta, M. K.*; Jin, M.*; Ding, J.*; Wu, J.*; Chen, Z.*; Lin, S.*; Fabelo, O.*; Rodriguez-Velamazan, J. A.*; Kofu, Maiko; et al.
Nature Materials, 22(8), p.999 - 1006, 2023/08
Times Cited Count:46 Percentile:99.16(Chemistry, Physical)Hashimoto, Shunsuke*; Yamaguchi, Satoshi*; Harada, Masashi*; Nakajima, Kenji; Kikuchi, Tatsuya*; Oishi, Kazuki*
Journal of Colloid and Interface Science, 638, p.475 - 486, 2023/05
Times Cited Count:6 Percentile:68.06(Chemistry, Physical)Recently, it has been reported that anomalous improvement in the thermal conductivity of nanofluid composed of base liquids and dispersed solid nanoparticles, compared to the theoretically predicted value calculated from the particle fraction. Generally, the thermal conductivity values of gases and liquids are dominated by the mean free path of the molecules during translational motion. Herein, we present solid evidence showing the possible contribution of the vibrational behavior of liquid molecules around nanoparticles to increasing these thermal conductivities.
Wu, P.*; Murai, Naoki; Li, T.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Kofu, Maiko; Nakajima, Kenji; Xia, K.*; Peng, K.*; Zhang, Y.*; et al.
New Journal of Physics (Internet), 25(1), p.013032_1 - 013032_11, 2023/01
Times Cited Count:0 Percentile:0.00(Physics, Multidisciplinary)Iwasa, Kazuaki*; Suyama, Kazuya*; Kawamura, Seiko; Nakajima, Kenji; Raymond, S.*; Steffens, P.*; Yamada, Akira*; Matsuda, Tatsuma*; Aoki, Yuji*; Kawasaki, Ikuto; et al.
Physical Review Materials (Internet), 7(1), p.014201_1 - 014201_11, 2023/01
Times Cited Count:3 Percentile:51.61(Materials Science, Multidisciplinary)Nakajima, Kenji; Kikuchi, Tatsuya*; Kawamura, Seiko; Kambara, Wataru*
EPJ Web of Conferences, 272, p.02012_1 - 02012_8, 2022/11
We will present some of attempts on AMATEAS, a cold-neutron chopper spectrometer at a pulsed source, to increase time-windows at a single-measurement condition. One of ways is that, by allowing interveined trajectories on the time-of-flight diagram, the usable width selectable for is can be increased. Based on our experiences, the conditions of pulse repetition rate multiplication based polychromatic measurements on chopper spectrometers at pulsed sources will be discussed. Optimization of wide-band polychromatic measurements and a generalized formulated condition will be proposed. Application of our idea to existing spectrometers and to the criteria design of an optimized chopper spectrometer will be also discussed with suggesting further possibility to improve efficiency by modifying the pulse shaping chopper.
Luo, P.*; Zhai, Y.*; Falus, P.*; Garca Sakai, V.*; Hartl, M.*; Kofu, Maiko; Nakajima, Kenji; Faraone, A.*; Z, Y.*
Nature Communications (Internet), 13, p.2092_1 - 2092_9, 2022/04
Times Cited Count:7 Percentile:67.21(Multidisciplinary Sciences)Mattan, K.*; Ono, Toshio*; Kawamura, Seiko; Nakajima, Kenji; Nambu, Yusuke*; Sato, Taku*
Physical Review B, 105(13), p.134403_1 - 134403_8, 2022/04
Times Cited Count:3 Percentile:33.99(Materials Science, Multidisciplinary)Spin dynamics of the spin-1/2 kagome-lattice antiferromagnet CsCuSnF was studied using high-resolution, time-of-flight inelastic neutron scattering. The flat mode, a characteristic of the frustrated kagome antiferromagnet, and the low-energy dispersive mode, which is dominated by magnons, can be well described by the linear spin-wave theory. However, the theory fails to describe three weakly dispersive modes between 9 and 14 meV. These modes could be attributed to two-spinon bound states, which decay into free spinons away from the zone center and at a high temperature, giving rise to continuum scattering.
Rathore, E.*; Juneja, R.*; Sarkar, D.*; Roychowdhury, S.*; Kofu, Maiko; Nakajima, Kenji; Singh, A. K.*; Biswas, K.*
Materials Today Energy (Internet), 24, p.100953_1 - 100953_9, 2022/03
Times Cited Count:18 Percentile:85.09(Chemistry, Physical)Yang, J.*; Ren, W.*; Zhao, X.*; Kikuchi, Tatsuya*; Miao, P.*; Nakajima, Kenji; Li, B.*; Zhang, Z.*
Journal of Materials Science & Technology, 99, p.55 - 60, 2022/02
Times Cited Count:9 Percentile:53.39(Materials Science, Multidisciplinary)High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices, differing from traditional alloys. Here, we investigate magnetic and thermal transport properties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical properties measurements and neutron scattering. Direct-current (dc) and alternating-current (ac) magnetizations measurements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic interactions in the entire temperature region and three anomalies are found at about 80, 50, and 20 K, which are related to the paramagnetic to antiferromagnetic transition, the antiferromagnetic to ferromagnetic transition, and the spin freezing, respectively. The electrical and thermal conductivities are significantly reduced compared to Ni and the temperature dependence of lattice thermal conductivity exhibits a glass-like plateau. Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.
Kojima, Yuki*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Nakajima, Kenji
Physical Review B, 105(2), p.L020408_1 - L020408_6, 2022/01
Times Cited Count:5 Percentile:52.19(Materials Science, Multidisciplinary)We report the neutron scattering results on magnetic orderings and excitations in BaCoTeO composed of two almost isolated subsystems A and B, which are described as an triangular Heisenberg-like antiferromagnet and a frustrated honeycomb Ising-like antiferromagnet, respectively. It was found that the excitation spectra of both subsystems are well separated and independent of each other. The excitation spectrum of subsystem A is composed of two single-magnon branches with roton-like minima at the M point and a clearly structured intense continuum, as similarly observed in BaCoSbO, which is strongly indicative of spinon excitations. Dispersion curves for subsystem B can be described by linear spin wave theory within the third-neighbor exchange interaction.
Hashimoto, Shunsuke*; Nakajima, Kenji; Kikuchi, Tatsuya*; Kamazawa, Kazuya*; Shibata, Kaoru; Yamada, Takeshi*
Journal of Molecular Liquids, 342, p.117580_1 - 117580_8, 2021/11
Times Cited Count:3 Percentile:20.58(Chemistry, Physical)Quasi-elastic neutron scattering (QENS) and pulsed-field-gradient nuclear magnetic resonance (PFGNMR) analyses of a nanofluid composed of silicon dioxide (SiO) nanoparticles and a base fluid of ethylene glycol aqueous solution were performed. The aim was to elucidate the mechanism increase in the thermal conductivity of the nanofluid above its theoretical value. The obtained experimental results indicate that SiO particles may decrease the self-diffusion coefficient of the liquid molecules in the ethylene glycol aqueous solution because of their highly restricted motion around these nanoparticles. At a constant temperature, the thermal conductivity increases as the self-diffusion coefficient of the liquid molecules decreases in the SiO nanofluids.
Okuma, Ryutaro*; Kofu, Maiko; Asai, Shinichiro*; Avdeev, M.*; Koda, Akihiro*; Okabe, Hirotaka*; Hiraishi, Masatoshi*; Takeshita, Soshi*; Kojima, Kenji*; Kadono, Ryosuke*; et al.
Nature Communications (Internet), 12, p.4382_1 - 4382_7, 2021/07
Times Cited Count:8 Percentile:63.05(Multidisciplinary Sciences)Kofu, Maiko; Watanuki, Ryuta*; Sakakibara, Toshiro*; Kawamura, Seiko; Nakajima, Kenji; Matsuura, Masato*; Ueki, Takeshi*; Akutsu, Kazuhiro*; Yamamuro, Osamu*
Scientific Reports (Internet), 11(1), p.12098_1 - 12098_8, 2021/06
Times Cited Count:5 Percentile:49.29(Multidisciplinary Sciences)Kawakita, Yukinobu; Kikuchi, Tatsuya*; Tahara, Shuta*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Maruyama, Kenji*; Yamauchi, Yasuhiro*; Kawamura, Seiko; Nakajima, Kenji
JPS Conference Proceedings (Internet), 33, p.011071_1 - 011071_6, 2021/03
CuI is a well-known superionic conductor in a high temperature solid phase where the mobile cations migrate between interstitial sites in the f.c.c. sublattice formed by iodine ions. Even in the molten state, it shows several features suggesting collective or cooperative ionic motion. MD results show that Cu diffuses much faster than I. The Cu-Cu partial structure factor have a FSDP which indicates a medium-range ordering of Cu ions. Moreover the Cu-Cu partial pair distribution deeply penetrates into the nearest neighboring Cu-I shell. To reveal origin such anomalous behaviors of molten CuI, we performed quaiselastic neutron scattering (QENS) by the disk-chopper spectrometer AMATERAS at MLF, J-PARC. To interpret the total dynamic structure factor obtained from coherent QENS, the mode distribution analysis was applied. It is found that the motion of iodine is a kind of fluctuating within an almost local area while Cu ions diffuse much faster than iodine ions.
Nakajima, Kenji; Kawamura, Seiko; Kofu, Maiko; Murai, Naoki; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Wakai, Daisuke*
JPS Conference Proceedings (Internet), 33, p.011089_1 - 011089_7, 2021/03
The recent update of AMATERAS, a cold-neutron disk-chopper spectrometer at Japan Proton Accelerator Research Complex (J-PARC), is reported. AMATERAS has been operating for a decade. Since 2017, some updates have been done or are underway, which include installing new detectors, replacing the vacuum system of the scattering chamber, and other works. We are also working on the re-investigation of the resolution function. Demonstration measurements were carried out at 1MW test operations done in 2018 and 2019. Plans of upgrading the spectrometer are currently being considered.
Nakagawa, Hiroshi; Yonetani, Yoshiteru*; Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Kataoka, Mikio*; Kono, Hidetoshi*
JPS Conference Proceedings (Internet), 33, p.011101_1 - 011101_6, 2021/03
Hydration water dynamics were measured by quasi-elastic neutron scattering with HnO/DO contrast for two DNA dodecamers, 5'CGCGCGCG'3 and 5'CGCGCGCG'3, which have been computationally shown to be structurally rigid and flexible, respectively. The dynamical transitions of the hydration water as well as DNA were observed for both sequences at approximately 240 K. Above the transition temperature, the mean square displacements of the hydration water for the rigid sequence were smaller than those for the flexible one. Furthermore, the relaxation time of the hydration water was longer in the rigid DNA than in the flexible DNA. We suggest that hydration water dynamics on the picosecond timescale are associated with sequence-dependent deformability of DNA.