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Journal Articles

Discovery of Early Paleocene (Danian) tuff from the Yezo Group in the Yubari area, Hokkaido, Northeast Japan

Kubomi, Ko*; Nagata, Mitsuhiro; Ota, Hiroto*; Miyata, Kazunori*; Oto, Shigeru*

Chishitsugaku Zasshi (Internet), 129(1), p.453 - 460, 2023/09

The Hakobuchi Formation in Hokkaido, NE Japan, consists of marine to terrestrial clastic rocks of the uppermost part of the Yezo Group, was previously interpreted to range from Early Campanian to Late Paleocene age, with a hiatus near the K/Pg boundary. No definitive evidence of the depositional age indicating Lower Paleocene (Danian) has been reported from the formation so far. We reported the LA-ICPMS zircon U-Pb dates of a tuff layer of the Hakobuchi Formation in the Yubari area. The weighted average date of the youngest cluster was 64.1 $$pm$$ 1.1 Ma (2$$sigma$$), suggesting the depositional age of the formation is Danian. The result is the first radiometric evidence indicating that the Hakobuchi Formation, at least partly, is correlated with the Danian, and is essential to discuss the depositional age of the Hakobuchi Formation and geochronology of the Yezo Group.

Journal Articles

Magnetism of Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ with andalusite structure

Kakimoto, Kazuo*; Takada, Saki*; Ota, Hiroto*; Hayaguchi, Yuya*; Hagihara, Masato; Torii, Shuki*; Kamiyama, Takashi*; Mitamura, Hiroyuki*; Tokunaga, Masashi*; Hatakeyama, Atsushi*; et al.

Journal of the Physical Society of Japan, 91(5), p.054704_1 - 054704_7, 2022/05

 Times Cited Count:1 Percentile:35.17(Physics, Multidisciplinary)

Journal Articles

Sinusoidal magnetic structure of andalusite-type AlxFe$$_{2}$$-xGeO$$_{5}$$ with $$x$$ = 0.09 and 0.15

Kakimoto, Kazuo*; Ota, Hiroto*; Haraguchi, Yuya*; Hagihara, Masato; Torii, Shuki*; Kamiyama, Takashi*; Katori, Hiroko*

Journal of the Physical Society of Japan, 91(5), p.054707_1 - 054707_9, 2022/05

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Study of neutron-nuclear spin correlation term with a polarized Xe target

Sakai, Kenji; Oku, Takayuki; Okudaira, Takuya; Kai, Tetsuya; Harada, Masahide; Hiroi, Kosuke; Hayashida, Hirotoshi*; Kakurai, Kazuhisa*; Shimizu, Hirohiko*; Hirota, Katsuya*; et al.

JPS Conference Proceedings (Internet), 33, p.011116_1 - 011116_6, 2021/03

In neutron fundamental physics, study of correlation term $${bf s}cdot{bf I}$$ of a neutron spin $${bf s}$$ and a target nuclear spin $${bf I}$$ is important because $${bf s}cdot{bf I}$$ term interferes to parity non-conserving (PNC) and time reversal non-conserving terms. For this study, a xenon (Xe) is an interesting nucleus because it has been observed an enhancement of PNC effect around neutron resonance peaks, and polarizes up to $$ sim 10^{-1}$$ by using a spin exchange optical pumping (SEOP) method. We would plan to develop a polarized Xe gas target with a compact in-situ SEOP system, and to study $${bf s}cdot{bf I}$$ term by utilizing epithermal neutron beams supplied from a high intense pulsed spallation neutron source. As the first step, we attempted to measure neutron polarizing ability caused by $${bf s}cdot{bf I}$$ term at a 9.6 eV s-wave resonance peak of $$^{129}$$Xe at BL10 in MLF, by detecting change $$Delta R$$ of ratio between neutron transmissions with the polarized and unpolarized Xe target. After demonstrating that our apparatus could detect small change ($$Delta R_{rm DB} , {approx},10^{-2}$$) of neutron transmissions caused by Doppler broadening effect, a signified value of $$Delta R$$ has been obtained as preliminary results. For analyzing the obtained $$Delta R$$ in detail, we are improving our nuclear magnetic resonance and electron paramagnetic resonance systems for evaluating Xe polarization independently of neutron beams.

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.42(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

Pressure dependence of ferromagnetic phase boundary in BaVSe$$_3$$ studied with high-pressure $$mu^+$$SR

Sugiyama, Jun; Higemoto, Wataru; Andreica, D.*; Forslund, O. K.*; Nocerino, E.*; M${aa}$nsson, M.*; Sassa, Y.*; Gupta, R.*; Khasanov, R.*; Ota, Hiroto*; et al.

Physical Review B, 103(10), p.104418_1 - 104418_10, 2021/03

 Times Cited Count:6 Percentile:62.83(Materials Science, Multidisciplinary)

The magnetic nature of a quasi-one-dimensional compound, BaVSe$$_3$$, has been investigated with positive muon spin rotation and relaxation measurements at ambient and high pressures. At ambient pressure, the spectrum recorded under zero external magnetic field exhibited a clear oscillation below the Curie temperature due to the formation of quasistatic ferromagnetic order. As pressure increased from ambient pressure, $$T_{C}$$ was found to decrease slightly up to about 1.5 GPa, at which point $$T_{C}$$ started to increase rapidly with the further increase of the pressure. Based on a strong ferromagnetic interaction along the $$c$$-axis, the result revealed that there are two magnetic interactions in the ab-plane.

Journal Articles

Development and application of a $$^3$$He neutron spin filter at J-PARC

Okudaira, Takuya; Oku, Takayuki; Ino, Takashi*; Hayashida, Hirotoshi*; Kira, Hiroshi*; Sakai, Kenji; Hiroi, Kosuke; Takahashi, Shingo*; Aizawa, Kazuya; Endo, Hitoshi*; et al.

Nuclear Instruments and Methods in Physics Research A, 977, p.164301_1 - 164301_8, 2020/10

 Times Cited Count:9 Percentile:82.12(Instruments & Instrumentation)

Journal Articles

An Experimental setup for creating and imaging $$^{4}$$He$$_{2}$$$$^{ast}$$ excimer cluster tracers in superfluid helium-4 via neutron-$$^{3}$$He absorption reaction

Sonnenschein, V.*; Tsuji, Yoshiyuki*; Kokuryu, Shoma*; Kubo, Wataru*; Suzuki, So*; Tomita, Hideki*; Kiyanagi, Yoshiaki*; Iguchi, Tetsuo*; Matsushita, Taku*; Wada, Nobuo*; et al.

Review of Scientific Instruments, 91(3), p.033318_1 - 033318_12, 2020/03

 Times Cited Count:0 Percentile:0(Instruments & Instrumentation)

Journal Articles

Recent progress on practical materials study by Bragg edge imaging at J-PARC

Oikawa, Kenichi; Su, Y.; Kiyanagi, Ryoji; Kawasaki, Takuro; Shinohara, Takenao; Kai, Tetsuya; Hiroi, Kosuke; Harjo, S.; Parker, J. D.*; Matsumoto, Yoshihiro*; et al.

Physica B; Condensed Matter, 551, p.436 - 442, 2018/12

 Times Cited Count:5 Percentile:27.01(Physics, Condensed Matter)

Journal Articles

Time-of-flight neutron transmission imaging of martensite transformation in bent plates of a Fe-25Ni-0.4C alloy

Su, Y.; Oikawa, Kenichi; Shinohara, Takenao; Kai, Tetsuya; Hiroi, Kosuke; Harjo, S.; Kawasaki, Takuro; Gong, W.; Zhang, S. Y.*; Parker, J. D.*; et al.

Physics Procedia, 88, p.42 - 49, 2017/06

 Times Cited Count:4 Percentile:85.78

Journal Articles

Criteria for performance evaluation and numerical verification to shock-resistant design of buildings

Nishida, Akemi; Mukai, Yoichi*; Hamamoto, Takuji*; Kushibe, Atsumichi*; Komuro, Masato*; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Tsubota, Haruji

Proceedings of 12th International Conference on Shock and Impact Loads on Structures (SI 2017) (USB Flash Drive), p.379 - 388, 2017/06

Some design examples are presented to evaluate the shock-resistant performance of target buildings to confirm the applicability of the design criteria of AIJ guideline. Dynamic analyses are performed using SDOF model of an individual member on which an impulsive load is acting. Furthermore, analyses are performed using finite element model for the same member, and the results are compared to the results of the corresponding SDOF model for validation. Frame building structure model which is supposed to be located at the corner of a crossroad is investigated as an example. Dynamic responses and the corresponding damage states are illustrated for this building subjected to shock loads due to road vehicle crashes. As a non-structure member case, examples of window glass destruction subjected to internal and external gas explosions are presented.

Journal Articles

Superdeformation in $$^{35}$$S

Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Kobayashi, Motoki*; Kisamori, Keiichi*; Takaki, Motonobu*; Miya, Hiroyuki*; Ota, Shinsuke*; Michimasa, Shinichiro*; Shimoura, Susumu*; et al.

JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06

Journal Articles

Design examples

Nishida, Akemi; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Takeuchi, Yoshitaka*; Kano, Toshiya*; Ryuzaki, Hibiki*; Ota, Toshiro*; Kishi, Tokumitsu*; Komuro, Masato*; Nakamura, Naohiro*

Kenchikubutsu No Taishogeki Sekkei No Kangaekata, p.161 - 202, 2015/01

Though design guidelines for earthquake and wind loads are specified for buildings, the guideline for impulsive load as explosion and impact is not specified yet in architectural field. This document corresponds to Chapter 8 of the book titled "Introduction to Shock-Resistant Design of Buildings" which made towards the impact design guideline. Some design examples are presented to illustrate the applicability of the tentative guideline for impulsive loads. Two buildings - a steel frame and a reinforced concrete frame building structures - located at the corner of a crossroads are selected. Dynamic responses and the corresponding damage states are illustrated for the cases of two buildings subjected to impact loads due to road vehicle crashes, internal and external explosions. The idea has been shown in this document are those that can be applied to nuclear facilities.

Journal Articles

High-magnetic-field X-ray absorption and magnetic circular dichroism spectroscopy in the mixed-valent compound YbAgCu$$_4$$

Nakamura, Toshiyuki*; Matsuda, Yasuhiro*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(11), p.114702_1 - 114702_11, 2012/11

 Times Cited Count:11 Percentile:58(Physics, Multidisciplinary)

The X-ray absorption and magnetic circular dichroism (MCD) spectra at the Yb L$$_3$$ edge were measured in the mixed-valent heavy fermion compound YbAgCu$$_4$$ at high magnetic fields and low temperatures. The magnetic-field-temperature (H-T) phase boundary determined by the valence state is in very good agreement with that determined by the magnetization. It is clearly found that the metamagnetism of this compound is due to the field induced valence transition. A distinctive positive peak of the XMCD spectra appears in the vicinity of the white line of the absorption due to Yb$$^{3+}$$ state, while no feature is observed in the XMCD spectra corresponding to the Yb$$^{2+}$$ state. A small negative XMCD peak was observed at a lower energy and was attributed to the quadrupole trasition from theoretical calcuration, which explains its peculicar magnetic field dependence.

Journal Articles

Thermal spin pumping and magnon-phonon-mediated spin-Seebeck effect

Uchida, Kenichi*; Ota, Takeru*; Adachi, Hiroto; Xiao, J.*; Nonaka, Tatsumi*; Kajiwara, Yosuke*; Bauer, G. E. W.*; Maekawa, Sadamichi; Saito, Eiji

Journal of Applied Physics, 111(10), p.103903_1 - 103903_11, 2012/05

 Times Cited Count:121 Percentile:96.13(Physics, Applied)

Journal Articles

Current status of a new polarized neutron reflectometer at the intense pulsed neutron source of the Materials and Life Science Experimental Facility (MLF) of J-PARC

Takeda, Masayasu; Yamazaki, Dai; Soyama, Kazuhiko; Maruyama, Ryuji; Hayashida, Hirotoshi; Asaoka, Hidehito; Yamazaki, Tatsuya; Kubota, Masato; Aizawa, Kazuya; Arai, Masatoshi; et al.

Chinese Journal of Physics, 50(2), p.161 - 170, 2012/04

Journal Articles

Valence fluctuation in YbAgCu$$_4$$ at high Magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(1), p.015002_1 - 015002_2, 2012/01

 Times Cited Count:11 Percentile:58(Physics, Multidisciplinary)

The valence change of Yb ion in YbAgCu$$_4$$ was measured by means of X-ray absorption spectroscopy under high magnetic fields up to 35T. The valence state of Yb in YbAgCu$$_4$$ at 4.8K significantly increases at the metamagnetic transition. The saturation value of $$v$$ at 55T is evaluated as 2.97 using the relation $$Delta M/Delta v$$ at 35T. This value is in good agreement with $$v$$ for the related compound YbInCu$$_4$$ at high temperatures and the Yb valence in the localized high-field phase. We conclude that the metamagnetic transition in YbAgCu$$_4$$ arises from the valence transition, as theoretically predicted.

Journal Articles

Long-range spin Seebeck effect and acoustic spin pumping

Uchida, Kenichi*; Adachi, Hiroto; An, Toshu*; Ota, Takeru*; Toda, Masaya*; Hillebrands, B.*; Maekawa, Sadamichi; Saito, Eiji

Nature Materials, 10(10), p.737 - 741, 2011/10

 Times Cited Count:222 Percentile:98.46(Chemistry, Physical)

We show that, using a NiFe/Pt bilayer wire on an insulating sapphire plate, electrons in the wire recognize their position on the sapphire. Under a temperature gradient in the sapphire, surprisingly, the voltage generated in the Pt layer is shown to reflect the wire position, although the wire is isolated both electrically and magnetically. This non-local voltage due to the coupling of spins and phonons: the only possible carrier of information in this system. We demonstrate this coupling by directly injecting sound waves, which realizes the acoustic spin pumping. Our finding provides a persuasive answer to the long-range nature of the spin Seebeck effect, and it opens the door to "acoustic spintronics" in which sound waves are exploited for constructing spin-based devices.

Journal Articles

Spin Seebeck insulator

Uchida, Kenichi*; Xiao, J.*; Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Ieda, Junichi; Ota, Takeru*; Kajiwara, Yosuke*; Umezawa, Hiromitsu*; Kawai, Hirotaka*; et al.

Nature Materials, 9(11), p.894 - 897, 2010/11

 Times Cited Count:1023 Percentile:99.88(Chemistry, Physical)

Thermoelectric generation is an essential function in future energy-saving technologies. However, it has so far been an exclusive feature of electric conductors, a situation which limits its application; conduction electrons are often problematic in the thermal design of devices. Here we report electric voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, the magnetic insulator LaY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ can convert a heat flow into a spin voltage. Attached Pt films can then transform this spin voltage into an electric voltage as a result of the inverse spin Hall effect. The experimental result require us to introduce a thermally activated interface spin exchange between LaY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect.

Journal Articles

Observation of longitudinal spin-Seebeck effect in magnetic insulators

Uchida, Kenichi*; Adachi, Hiroto; Ota, Takeru*; Nakayama, Hiroyasu*; Maekawa, Sadamichi; Saito, Eiji

Applied Physics Letters, 97(17), p.172505_1 - 172505_3, 2010/10

 Times Cited Count:602 Percentile:99.68(Physics, Applied)

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