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論文

Enhancement of domain-wall mobility detected by NMR at the angular momentum compensation temperature

今井 正樹; 中堂 博之; 松尾 衛; 前川 禎通; 齊藤 英治

Physical Review B, 102(1), p.014407_1 - 014407_5, 2020/07

https://doi.org/10.1103/PhysRevB.102.014407
 被引用回数：1 パーセンタイル：100(Materials Science, Multidisciplinary)

The angular momentum compensation temperature $$T_{rm A}$$ of ferrimagnets has attracted much attention because of high-speed magnetic dynamics near $$T_{rm A}$$. We show that NMR can be used to investigate domain wall dynamics near $$T_{rm A}$$ in ferrimagnets. We performed $$^{57}$$Fe-NMR measurements on the ferrimagnet Ho$$_3$$Fe$$_5$$O$$_{12}$$ with $$T_{rm A}$$ = 245 K. In a multi-domain state, the NMR signal is enhanced by domain wall motion. We found that the NMR signal enhancement shows a maximum at $$T_{rm A}$$ in the multi-domain state. The NMR signal enhancement occurs due to increasing domain-wall mobility toward $$T_{rm A}$$. We develop the NMR signal enhancement model involves domain-wall mobility. Our study shows that NMR in multi-domain state is a powerful tool to determine $$T_{rm A}$$, even from a powder sample and it expands the possibility of searching for angular momentum-compensated materials.

論文

Giant spin hydrodynamic generation in laminar flow

高橋 遼*; 中堂 博之; 松尾 衛; 針井 一哉*; 大沼 悠一*; 前川 禎通; 齊藤 英治

Nature Communications (Internet), 11, p.3009_1 - 3009_6, 2020/06

https://doi.org/10.1038/s41467-020-16753-0
 被引用回数：0 パーセンタイル：100(Multidisciplinary Sciences)

Hydrodynamic motion can generate a flux of electron-spin's angular momentum via the coupling between fluid rotation and electron spins. Such hydrodynamic generation, called spin hydrodynamic generation (SHDG), has recently attracted attention in a wide range of fields, especially in spintronics. Spintronics deals with spin-mediated interconversion taking place on a micro or nano scale because of the spin-diffusion length scale. To be fully incorporated into the interconversion, SHDG physics should also be established in such a minute scale, where most fluids exhibit a laminar flow. Here, we report electric voltage generation due to the SHDG in a laminar flow of a liquid-metal mercury. The experimental results show a scaling rule unique to the laminar-flow SHDG. Furthermore, its energy con- version efficiency turns out to be about 105 greater than of the turbulent one. Our findings reveal that the laminar-flow SHDG is suitable to downsizing and to extend the coverage of fluid spintronics.

論文

Observation of a $$Xi$$ bound state in the $$^{12}$$C$$(K^-, K^+)$$ reaction at 1.8 GeV/$$c$$

永江 知文*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 金原 慎二; 七村 拓野*; 成木 恵; et al.

AIP Conference Proceedings 2130, p.020015_1 - 020015_9, 2019/07

https://doi.org//10.1063/1.5118383

For the full understanding of baryon-baryon interactions in flavor $$SU(3)$$, the $$Xi N$$ interaction is the last missing piece of information. So far, we have revealed the $$Lambda N$$ interaction to be attractive ($$U_{Lambda} cong 30$$ MeV), and $$Sigma N$$ interaction to be repulsive in the medium to heavy mass-number region. The $$Lambda Lambda$$ bonding energy is weakly attractive. While we have a few experimental observations suggesting the $$Xi N$$ interaction would be attractive, there still exist large theoretical ambiguities weather it is attractive or not. Experimental determinations on the existence of bound states of $$Xi$$ hypernuclei by observing bound-state peaks are strongly awaited. In this report, a new preliminary result on the missing-mass spectrum of a $$^{12}$$C$$(K^-, K^+)$$ reaction, which strongly suggests the existence of $$Xi$$-hypernuclear bound states, is presented.

論文

Spin Seebeck mechanical force

針井 一哉; Seo, Y.-J.*; 堤 康雅*; 中堂 博之; 大柳 洸一*; 松尾 衛; 塩見 雄毅*; 小野 崇人*; 前川 禎通; 齊藤 英治

Nature Communications (Internet), 10(1), p.2616_1 - 2616_5, 2019/06

https://doi.org/10.1038/s41467-019-10625-y
 被引用回数：10 パーセンタイル：11.06(Multidisciplinary Sciences)

Electric current has been used to send electricity to far distant places. On the other hand, spin current, a flow of electron spin, can in principle also send angular momentum to distant places. In a magnet, there is a universal spin carrier called a spin wave, a wave-type excitation of magnetization. Since spin waves exhibit a long propagation length, it should be able to send angular momentum that can generate torque and force at a distant place: a new function of magnets. Here we observe mechanical angular momentum transmission and force generation due to spin waves injected into Y$$_3$$Fe$$_5$$O$$_{12}$$ by the spin-Seebeck effect. The spin-wave current, transmitted through a Y$$_3$$Fe$$_5$$O$$_{12}$$ micro cantilever, was found to create a mechanical force on the cantilever as a non-local reaction of the spin-Seebeck effect. Spin-wave current can be generated remotely even in open circuits, and it can be used to drive micro mechanical devices.

論文

Angular momentum compensation manipulation to room temperature of the ferrimagnet Ho$$_{3-x}$$Dy$$_{x}$$Fe$$_5$$O$$_{12}$$ detected by the Barnett effect

今井 正樹; 中堂 博之; 小野 正雄; 針井 一哉; 松尾 衛; 大沼 悠一*; 前川 禎通; 齊藤 英治

Applied Physics Letters, 114(16), p.162402_1 - 162402_4, 2019/04

https://doi.org/10.1063/1.5095166
 被引用回数：7 パーセンタイル：21.51(Physics, Applied)

We demonstrate that the angular momentum compensation temperature $$T_{rm A}$$, at which the net angular momentum in the sample disappears, can be controlled in Ho$$_3$$Fe$$_5$$O$$_{12}$$ by partially substituting Dy for Ho. The $$T_{rm A}$$ can be detected using the Barnett effect, by which mechanical rotation magnetizes an object due to spin-rotation coupling. We found that $$T_{rm A}$$ increases with the Dy content and clarified that the $$T_{rm A}$$ of Ho$$_{1.5}$$Dy$$_{1.5}$$Fe$$_5$$O$$_{12}$$ coincides with room temperature. The Barnett effect enables us to explore materials applicable to magnetic devices utilizing the angular momentum compensation only by rotating the powder sample at room temperature.

論文

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

江川 弘行; 足利 沙希子; 長谷川 勝一; 橋本 直; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 金原 慎二*; 七村 拓野; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02

https://doi.org/10.1093/ptep/pty149
 被引用回数：1 パーセンタイル：100(Physics, Multidisciplinary)

A double-$$Lambda$$ hypernucleus, $${}_{LambdaLambda}mathrm{Be}$$, was observed by the J-PARC E07 collaborationin nuclear emulsions tagged by the $$(K^{-},K^{+})$$ reaction. This event was interpreted as a production and decay of $$ {}_{LambdaLambda}^{;10}mathrm{Be}$$,$${}_{LambdaLambda}^{;11}mathrm{Be}$$, or $${}_{LambdaLambda}^{;12}mathrm{Be}^{*}$$ via $$Xi^{-}$$ capture in $${}^{16}mathrm{O}$$.By assuming the capture in the atomic 3D state, the binding energy of two $$Lambda$$ hyperons$$,$$($$B_{LambdaLambda}$$)of these double-$$Lambda$$ hypernuclei are obtained to be$$15.05 pm 0.11,mathrm{MeV}$$, $$19.07 pm 0.11,mathrm{MeV}$$, and $$13.68 pm 0.11,mathrm{MeV}$$, respectively. Based on the kinematic fitting, $${}_{LambdaLambda}^{;11}mathrm{Be}$$ is the most likely explanation for the observed event.

論文

Trapping probability of strangeness via $$mathrm{Xi}^{-}$$ hyperon capture at rest in nuclear emulsion

Theint, A. M. M.*; 江川 弘行; 吉田 純也; 他7名*

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D01_1 - 021D01_10, 2019/02

https://doi.org/10.1093/ptep/pty147
 被引用回数：2 パーセンタイル：45.7(Physics, Multidisciplinary)

In the E373 experiment at KEK-PS, we have located nearly $$2 times 10^{4}$$ stopping events of $$Xi^{-}$$ hyperon candidates in nuclear emulsion. Among them, the identification of $$Xi^{-}$$ hyperon was performed with Constant Sagitta (CS) method by measuring multiple Coulomb scattering for 695 clearly stopping events. With use of Geant4 simulation, the parameters for the CS method were optimised and we obtained the number of real $$Xi^{-}$$ stopping events to be $$432.3 pm 7.6^{+0.0}_{-14.0}$$ with 3.2% systematic error. The trapping probabilities of two $$Lambda$$ hyperons for light and heavy nuclei were found to be $$5.0 pm 1.7$$% and $$4.2 pm 1.4$$%, respectively. For at least one $$Lambda$$ trapping, the probabilities were $$69.4 pm 8.1$$% and $$51.1 pm 5.7$$% for light and heavy nuclei. These results are the first time to present the trapping probabilities of $$Lambda$$ hyperons via $$Xi^{-}$$ hyperon capture at rest in the emulsion.

論文

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

佐藤 哲也; 浅井 雅人; Borschevsky, A.*; Beerwerth, R.*; 金谷 佑亮*; 牧井 宏之; 水飼 秋菜*; 永目 諭一郎; 長 明彦; 豊嶋 厚史; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

https://doi.org/10.1021/jacs.8b09068
 被引用回数：13 パーセンタイル：26.3(Chemistry, Multidisciplinary)

第一イオン化エネルギー(IP$$_1$$)は、原子の価電子軌道に関する情報を与える。99番元素アインスタイニウムよりも重いアクチノイドのIP$$_1$$は、一度に一つの原子しか扱うことのできない実験の難しさから、これまでに実験的に測定された例はなかった。我々は表面電離法を応用した新しい測定手法により、103番元素ローレンシウム(Lr)のIP$$_1$$測定に成功し、Lrが弱く束縛された最外殻電子をもつことを強く示唆する結果を得た。一方、Lrとは対象的に、102番元素ノーベリウムは充填された5f軌道および7s軌道をもつために、アクチノイド中最高のIP$$_1$$をもつと考えられている。表面電離法によるIP$$_1$$決定法をNoおよび100番元素フェルミウム, 101番元素メンデレビウムに適用することにより求められた各IP$$_1$$から、5f軌道への電子の充填に伴ってIP$$_1$$が単調に増加し、Noで最も大きくなることを確かめることができた。このことから、f軌道に電子が充填され、アクチノイド系列がLrで終わることを実験的に確かめた。

論文

Observation of gyromagnetic reversal

今井 正樹; 緒方 裕大*; 中堂 博之; 小野 正雄; 針井 一哉; 松尾 衛*; 大沼 悠一*; 前川 禎通; 齊藤 英治

Applied Physics Letters, 113(5), p.052402_1 - 052402_3, 2018/07

https://doi.org/10.1063/1.5041464
 被引用回数：9 パーセンタイル：36.37(Physics, Applied)

We report direct observation of gyromagnetic reversal, which is the sign change of gyromagnetic ratio in a ferrimagnet Ho$$_3$$Fe$$_5$$O$$_{12}$$, by using the Barnett effect measurement technique at low temperatures. The Barnett effect is a phenomenon in which magnetization is induced by mechanical rotation through the coupling between rotation and total angular momentum $$J$$ of electrons. The magnetization of Ho$$_3$$Fe$$_5$$O$$_{12}$$ induced by mechanical rotation disappears at 135 K and 240 K. The temperatures correspond to the magnetization compensation temperature $$T_{rm M}$$ and the angular momentum compensation temperature $$T_{rm A}$$, respectively. Between $$T_{rm M}$$ and $$T_{rm A}$$, the magnetization flips over to be parallel against the angular momentum due to the sign change of gyromagnetic ratio. This study provides an unprecedented technique to explore the gyromagnetic properties.

論文

First determination of the level structure of an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; et al.

Physical Review Letters, 120(13), p.132505_1 - 132505_5, 2018/03

https://doi.org/10.1103/PhysRevLett.120.132505
 被引用回数：5 パーセンタイル：35.7(Physics, Multidisciplinary)

We report on the first observation of $$gamma$$ rays emitted from an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F. The energy spacing between the ground state doublet, $$1/2^+$$ and $$3/2^+$$ states, of $$^{19}_{Lambda}$$F is determined to be $$315.5pm0.4({rm stat.})^{+0.6}_{-0.5}({rm syst.})$$ keV by measuring the $$gamma$$-ray energy of the $$M1(3/2^+ to 1/2^+)$$ transition. In addition, three $$gamma$$-ray peaks are observed and assigned as $$E2(5/2^+ to 1/2^+)$$, $$E1(1/2^- to 1/2^+)$$, and $$E1(1/2^- to 3/2^+)$$ transitions. The excitation energies of the $$5/2^+$$ and $$1/2^-$$ states are determined to be $$895.2pm0.3({rm stat.})pm0.5({rm syst.})$$ keV and $$1265.6pm1.2({rm stat.})^{+0.5}_{-0.7}({rm syst.})$$ keV, respectively. It is found that the ground state doublet spacing is well described by theoretical models based on existing $$s$$- and $$p$$-shell hypernuclear data.

論文

Spectroscopy of nuclei with multi-strangeness by using new S-2S spectrometer at J-PARC

後神 利志*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 市川 裕大; 七村 拓野; 成木 恵; 佐甲 博之; et al.

JPS Conference Proceedings (Internet), 18, p.011031_1 - 011031_6, 2017/11

https://doi.org/10.7566/JPSCP.18.011031

The missing mass spectroscopy of $$Xi^-$$ hypernuclei is planned at the Japan Proton Accelerator Research Complex (J-PARC) by using the $$(K^-,K^+)$$ reaction. We are constructing a new magnetic spectrometer, S-2S, which has a better momentum resolution [$$Delta p/p = 5 times 10^{-4}$$ (FHWM)] than that of an existing spectrometer (SKS) at J-PARC. S-2S would give us an opportunity to confirm the existence of $$Xi^-$$ hypernuclei as a peak structure owing to both the high momentum resolution and its reasonably large solid angle. Brief descriptions of our experiment and of its preparation status are presentedin this article.

論文

Enhanced orbital magnetic moment in FeCo nanogranules observed by Barnett effect

緒方 裕大; 中堂 博之; Gu, B.; 小林 伸聖*; 小野 正雄; 針井 一哉; 松尾 衛; 齊藤 英治; 前川 禎通

Journal of Magnetism and Magnetic Materials, 442, p.329 - 331, 2017/11

https://doi.org/10.1016/j.jmmm.2017.06.101
 被引用回数：4 パーセンタイル：49.06(Materials Science, Multidisciplinary)

The gyroscopic g factor, $$g'$$, of FeCo nanogranules embedded in a matrix of MgF$$_2$$ (FeCo-MgF$$_2$$) was determined by measuring the magnetic-field generation from a rotating sample due to the Barnett effect. The $$g'$$ value of the FeCo-MgF$$_2$$ is estimated to be 1.76 $$pm$$ 0.11. The orbital contribution to the magnetic moment in the FeCo nanogranules was found to be quite large compared with that in bulk FeCo, being consistent with a density-functional-theory calculation that shows that the orbital magnetic moment may increase at the FeCo/MgF$$_2$$ interfaces. The result suggests that the orbital magnetic moment is enhanced by symmetry breaking at the surface of the FeCo nanogranules.

論文

$$gamma$$-ray spectroscopy of hypernuclei; Recent results and prospect at J-PARC

田村 裕和*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.011004_1 - 011004_11, 2017/07

https://doi.org/10.7566/JPSCP.17.011004

The present status and future prospects of precision $$gamma$$-ray spectroscopy of $$Lambda$$ hypernuclei are described. A new experiment (J-PARC E13) has been performed at the J-PARC K1.8 line employing a newly-developed germanium (Ge) detector array, Hyperball-J, via the $$(K^-,pi^-)$$ reaction on $$^4$$He and $$^{19}$$F targets. This is the first study of $$s$$-shell and $$sd$$-shell $$Lambda$$ hypernuclei with Ge detectors. The $$^4$$He target spectrum exhibited a $$gamma$$-ray peak of $$^4_{Lambda}{rm He}(1^+to 0^+)$$ at $$1.406 pm 0.002 pm 0.002$$ MeV. Compared with the energy ($$1.09 pm 0.02$$ MeV) of the corresponding transition for the mirror hypernucleus, $$^4_{Lambda}{rm H}(1^+to 0^+)$$, the present result clearly indicates a large charge symmetry breaking (CSB) effect. This decisive data for CSB allows a stringent test of baryon-baryon interaction models. As for the $$^{19}$$F target run, a preliminary spectrum shows several $$gamma$$-ray peaks assigned to $$^{19}_{Lambda}{rm F}$$ transitions. Future plans of $$gamma$$-ray spectroscopy are also discussed.

論文

Search for excited state of $$Sigma$$ hypernucleus in the J-PARC E13 experiment

中川 真菜美*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012009_1 - 012009_4, 2017/07

https://doi.org/10.7566/JPSCP.17.012009

One of the main items of the J-PARC E13 experiment is the search for excited states of the $$^4_{Sigma}$$He hypernucleus via the $$^4$$He$$(K^-,pi^-)$$ reaction at 1.5 GeV/c. The missing-mass spectrum of the $$^4$$He$$(K^-,pi^-)X$$ reaction was obtained in an angular range from 0 to 20 degrees. We show the count-base spectrum of the missing-mass in the angular range from 2 to 14 degrees. The ground state of $$^4_{Lambda}$$He and $$^4_{Sigma}$$He were clearly observed in the missing-mass spectrum. We also show three missing-mass spectra divided by the reaction angle.

論文

The First gamma-ray spectroscopic study of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012004_1 - 012004_4, 2017/07

https://doi.org/10.7566/JPSCP.17.012004

The first $$gamma$$-ray spectroscopy of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F, is performed in June, 2015 at the J-PARC K1.8 beam line (J-PARC E13). Precise energy levels of $$^{19}_{Lambda}$$F can be revealed by measured $$gamma$$ rays in this experiment. Especially, the strength of $$Lambda N$$ spin-spin interaction in $$sd$$-shell hypernucleus is obtained through the energy spacing of the ground-state doublet of the hypernucleus. By comparing its strength between the $$s$$, $$p$$, and $$sd$$-shell hypernuclei, a radial dependence $$Lambda N$$ interaction is investigated. The hypernucleus is produced through the $$(K^-,pi^-)$$ reaction with the beam momentum of 1.8 GeV/c. In very preliminary results, we observed two $$gamma$$ rays, and their energies are $$315.8 pm 0.4$$ keV and $$ 895.3 pm 0.3$$ keV where the uncertainties are only statistical.

論文

Observation of $$Xi$$ bound states in the $$^{12}$$C$$(K^-,K^+)X$$ reaction at 1.8 GeV/$$c$$ in J-PARC

永江 知文*; 江川 弘行; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 谷田 聖; et al.

Proceedings of Science (Internet), 7 Pages, 2017/05

https://pos.sissa.it/archive/conferences/281/038/INPC2016_038.pdf

We have carried out a pilot data taking of the J-PARC E05 experiment to search for the bound state peaks of $$^{12}_{Xi}$$Be in the $$^{12}$$C$$(K^-,K^+)X$$ reaction at 1.8 GeV/$$c$$. The measurement was performed at the K1.8 beam line of the J-PARC hadron experimental hall with a typical $$K^-$$ beam intensity of $$6 times 10^5$$ every six seconds. So far the best energy resolution of about 6 MeV FWHM was achieved with the existing SKS spectrometer. With a reasonable statistics, we have succeeded to observe peak structures in the bound region, which seems to suggest that the potential depth of $$Xi$$ would be deeper than 14 MeV estimated in the previous measurements.

論文

Gyroscopic $$g$$ factor of rare earth metals

緒方 裕大; 中堂 博之; 小野 正雄; 針井 一哉; 松尾 衛; 前川 禎通; 齊藤 英治

Applied Physics Letters, 110(7), p.072409_1 - 072409_4, 2017/02

https://doi.org/10.1063/1.4976998
 被引用回数：9 パーセンタイル：37.35(Physics, Applied)

We develop the $$in$$ $$situ$$ magnetization measurement apparatus for observing the Barnett effect consisting of a fluxgate sensor, high speed rotor with frequencies of up to 1.5 kHz, and magnetic shield at room temperature. The effective magnetic field (Barnett field) in a sample arising from rotation magnetizes the sample and is proportional to the rotational frequency. The gyroscopic $$g$$ factor, $$g'$$, of rare earth metals, in particular, Gd, Tb and Dy were estimated to be 2.00$$pm$$0.08, 1.53$$pm$$0.17, and 1.15$$pm$$0.32, respectively, from the slopes of the rotation dependence of the Barnett field. This study provides a technique to determine the $$g'$$ factor even in samples where the spectroscopic method may not be available.

論文

Study of the $$overline{K}$$-nucleus interaction by using the $$^{12}$$C(K$$^{-}$$, p) reaction at J-PARC

市川 裕大; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 金原 慎二; 中田 祥之; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 13, p.020007_1 - 020007_5, 2017/02

https://doi.org/10.7566/JPSCP.13.020007

これまで反K中間子と原子核の間の相互作用はK中間子原子(K-中間子と原子核の電磁相互作用による束縛状態)のX線を用いて研究が行われてきた。しかし、このK中間子原子のX線測定では理論モデルの種類によって結果が大きく依存するという問題がため、X線測定だけでは相互作用を決定することが困難である。そこで、われわれは$$^{12}$$C(K$$^{-}$$, p)反応におけるエネルギースペクトルを測定し、理論計算と比較する手法を用いて反K中間子と原子核の間の相互作用を決定しようとしている。この手法は既にKEK E548実験で行われているが、実験セットアップ上の問題点が指摘されているため、過去の高エネルギー加速器研究機構での実験では不十分である。そこで、われわれはJ-PARCにおいて再実験を行い、正しく$$^{12}$$C(K$$^{-}$$, p)のスペクトルを取得することに成功した。

論文

Spin hydrodynamic generation

高橋 遼*; 松尾 衛; 小野 正雄; 針井 一哉; 中堂 博之; 岡安 悟; 家田 淳一; 高橋 三郎*; 前川 禎通; 齊藤 英治

Nature Physics, 12, p.52 - 56, 2016/01

https://doi.org/10.1038/nphys3526
 被引用回数：44 パーセンタイル：5.98(Physics, Multidisciplinary)

Magnetohydrodynamic generation is the conversion of fluid kinetic energy into electricity. Such conversion, which has been applied to various types of electric power generation, is driven by the Lorentz force acting on charged particles and thus a magnetic field is necessary. On the other hand, recent studies of spintronics have revealed the similarity between the function of a magnetic field and that of spin-orbit interactions in condensed matter. This suggests the existence of an undiscovered route to realize the conversion of fluid dynamics into electricity without using magnetic fields. Here we show electric voltage generation from fluid dynamics free from magnetic fields; we excited liquid-metal flows in a narrow channel and observed longitudinal voltage generation in the liquid. This voltage has nothing to do with electrification or thermoelectric effects, but turned out to follow a universal scaling rule based on a spin-mediated scenario. The result shows that the observed voltage is caused by spin-current generation from a fluid motion: spin hydrodynamic generation. The observed phenomenon allows us to make mechanical spin-current and electric generators, opening a door to fluid spintronics.

論文

Barnett effect in paramagnetic states

小野 正雄; 中堂 博之; 針井 一哉; 岡安 悟; 松尾 衛; 家田 淳一; 高橋 遼*; 前川 禎通; 齊藤 英治

Physical Review B, 92(17), p.174424_1 - 174424_4, 2015/11

https://doi.org/10.1103/PhysRevB.92.174424
 被引用回数：16 パーセンタイル：32.98(Materials Science, Multidisciplinary)

We report the observation of the Barnett effect in paramagnetic states by mechanically rotating gadolinium (Gd) metal with a rotational frequency of up to 1.5 kHz above the Curie temperature. An in situ magnetic measurement setup comprising a high-speed rotational system and a fluxgate magnetic sensor was developed for the measurement. Temperature dependence of the observed magnetization follows that of paramagnetic susceptibility, indicating that any emergent magnetic field is proportional to the rotational frequency and is independent of temperature. From the proportionality constant of the emergent field, the gyromagnetic ratio of Gd is calculated to be -29 $$pm$$ 5 GHz/T. This study revisits the primordial issue of magnetism with modern technologies to shed new light on the fundamental spin-rotation coupling.

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