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論文

Observation of the angular momentum compensation by Barnett effect and NMR

中堂 博之; 今井 正樹; 松尾 衛; 前川 禎通; 齊藤 英治

Journal of the Physical Society of Japan, 90(8), p.081003_1 - 081003_11, 2021/08

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

We demonstrate observation of the angular momentum compensation temperature $$T_{rm A}$$, at which the net angular momentum is quenched in ferrimagnets. Using the Barnett effect, in which an object is magnetized by mechanical rotation owing to spin-rotation coupling, we measure $$T_{rm A}$$ in the Ho$$_{3-x}$$Dy$$_{x}$$Fe$$_{5}$$O$$_{12}$$ system. We determine $$T_{rm A}$$ to be 240 K in Ho$$_{3}$$Fe$$_{5}$$O$$_{12}$$ (HoIG). We find that $$T_{rm A}$$ increases with Dy content and show that $$T_{rm A}$$ of Ho$$_{1.5}$$Dy$$_{1.5}$$Fe$$_{5}$$O$$_{12}$$ corresponds with room temperature. We also demonstrate that $$^{57}$$Fe-NMR measurements can be applied to explore domain wall dynamics in HoIG. We find that the NMR intensity exhibits a maximum at $$T_{rm A}$$ in the multi-domain state. We provide a simple model for describing this NMR signal enhancement caused by enhancement of domain-wall mobility at $$T_{rm A}$$.

論文

Barnett field, rotational Doppler effect, and Berry phase studied by nuclear quadrupole resonance with rotation

中堂 博之; 松尾 衛*; 前川 禎通*; 齊藤 英治

Physical Review B, 103(17), p.174308_1 - 174308_10, 2021/05

 被引用回数:0 パーセンタイル:0(Materials Science, Multidisciplinary)

We report the observation of the Barnett field, rotational Doppler effect, and Berry phase using the rotating nuclear quadrupole resonance (NQR) methods. We have developed coil-spinning techniques that enable us to systematically study the effects of rotation in setups involving rotation of the signal detector, rotation of the sample, and simultaneous rotation of both the signal detector and sample. Applying these setups to NQR measurements, we observe NQR line splittings in which the spectral structures are clearly distinct among the setups. By analyzing these structures, we clarify the origin of the NQR line splittings and discuss the relationship between the rotational Doppler effect, Barnett field effect, and Berry phase in terms of the rotational degrees of freedom, such as the relative rotation and the sample rotation itself, and the observation frame of reference. We also provide clear evidence of the difference between the rotational Doppler effect and the Barnett field, and the equivalence of the Barnett field and the Berry phase.

報告書

東海再処理施設周辺の環境放射線モニタリング結果; 2019年度

中野 政尚; 藤井 朋子; 根本 正史; 飛田 慶司; 瀬谷 夏美; 西村 周作; 細見 健二; 永岡 美佳; 横山 裕也; 松原 菜摘; et al.

JAEA-Review 2020-069, 163 Pages, 2021/02

JAEA-Review-2020-069.pdf:4.78MB

核燃料サイクル工学研究所では、「日本原子力研究開発機構核燃料サイクル工学研究所再処理施設保安規定、第IV編 環境監視」に基づき、再処理施設周辺の環境放射線モニタリングを実施している。本報告書は、2019年4月から2020年3月までの間に実施した環境放射線モニタリングの結果、及び大気、海洋への放射性物質の放出に起因する周辺公衆の線量算出結果について、取りまとめたものである。なお、上記の環境放射線モニタリングの結果において、2011年3月に発生した東京電力(2016年4月1日付けで東京電力ホールディングスに変更)福島第一原子力発電所事故で放出された放射性物質の影響が多くの項目でみられた。また、環境監視計画の概要、測定方法の概要、測定結果及びその経時変化、気象統計結果、放射性廃棄物の放出状況、平常の変動幅の上限値を超過した値の評価について付録として収録した。

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

 被引用回数:4 パーセンタイル:68.88(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

 被引用回数:4 パーセンタイル:63.95(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

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

 被引用回数:14 パーセンタイル:83.38(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

Coolability evaluation of debris bed on core catcher in a sodium-cooled fast reactor

松尾 英治*; 佐々 京平*; 小山 和也*; 山野 秀将; 久保 重信; Hourcade, E.*; Bertrand, F.*; Marie, N.*; Bachrata, A.*; Dirat, J. F.*

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05

炉心損傷事故(CDA)時に炉心から排出される溶融燃料は、下部ナトリウムプレナムで燃料冷却材相互作用により固化した粒子デブリになり、そのデブリは、原子炉容器の下部にあるコアキャッチャー上にベッドを形成する可能性がある。デブリベッドの冷却性評価は、コアキャッチャーの設計に必要である。本研究の目的は、ASTRID設計のために、コアキャッチャー上のデブリベッドの冷却性を評価することである。この目的のための第一歩として、デブリベッドのみをモデル化することにより、短期間及び後期の間に形成されたデブリベッドの冷却性計算が実施された。したがって、コアキャッチャーの設計及び崩壊熱除去系の詳細は、本論文では述べていない。全ての計算において、デブリベッド近くの冷却材温度はパラメータである。計算ツールは、一次元プラント動特性解析コード、Super-COPDに組み込まれたデブリベッドモジュールである。その評価は、短期間及び後期の間に形成されたデブリベッドが、コールドプール中のコアキャッチャー近くの十分な冷却材流量を確保する設計により冷却可能となることを示している。

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

 被引用回数:11 パーセンタイル:77.53(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 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

 被引用回数:12 パーセンタイル:69.15(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

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

 被引用回数:5 パーセンタイル:57.14(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

熱スピン相互変換

大沼 悠一; 松尾 衛*; 前川 禎通; 齊藤 英治

まぐね, 12(5), p.217 - 224, 2017/10

熱とスピンの相互変換現象であるスピンゼーベック効果及びスピンペルチェ効果について微視的理論に基づき議論を行う。まずはじめに、熱流からスピン流を生成するスピンゼーベック効果について議論する。スピンゼーベック効果の最近の進展を紹介し、フェリ磁性体でのスピンゼーベック効果の符号反転について説明する。次に、スピン流による熱流生成法であるスピンペルチェ効果について議論する。最後に、スピンゼーベック効果とスピンペルチェ効果がオンサーガの相反関係によってまとめられることを示し、スピンと熱の輸送に関するケルビンの関係式を導出する。

論文

Spin current generation using a surface acoustic wave generated via spin-rotation coupling

小林 大眞*; 吉川 智英*; 松尾 衛*; 井口 亮*; 前川 禎通; 齊藤 英治; 能崎 幸雄*

Physical Review Letters, 119(7), p.077202_1 - 077202_5, 2017/08

 被引用回数:58 パーセンタイル:96.25(Physics, Multidisciplinary)

We demonstrate the generation of alternating spin current (SC) via spin-rotation coupling (SRC) using a surface acoustic wave (SAW) in a Cu film. Ferromagnetic resonance caused by injecting SAWs was observed in a Ni-Fe film attached to a Cu film, with the resonance further found to be suppressed through the insertion of a SiO$$_{2}$$ film into the interface. The intensity of the resonance depended on the angle between the wave vector of the SAW and the magnetization of the Ni-Fe film. This angular dependence is explicable in terms of the presence of spin transfer torque from a SC generated via SRC.

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

 被引用回数:11 パーセンタイル:60.64(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

Spin-mechatronics

松尾 衛; 齊藤 英治; 前川 禎通

Journal of the Physical Society of Japan, 86(1), p.011011_1 - 011011_7, 2017/01

 被引用回数:17 パーセンタイル:80.77(Physics, Multidisciplinary)

物体の機械運動に伴う力学的角運動量を用いたスピン制御およびスピン流生成の理論とその実証実験に関する我々の最新の研究成果をまとめた解説論文(Invited review paper)である。

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

 被引用回数:65 パーセンタイル:95.17(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

 被引用回数:19 パーセンタイル:68.15(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.

論文

Line splitting by mechanical rotation in nuclear magnetic resonance

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

Japanese Journal of Applied Physics, 54(5), p.050302_1 - 050302_3, 2015/05

 被引用回数:10 パーセンタイル:48.8(Physics, Applied)

Nuclear magnetic resonance (NMR) measurements for a nuclear spin 1/2 system in an external magnet field and mechanical rotation in kHz range are reported. NMR signals are measured by the synchronous rotation of a sample and a detector coil under the condition that the rotation axis is perpendicular to the external field. NMR line splits into two despite the system having a single Zeeman level separation. We analytically show that the splitting originates in the nuclear spin motion under mechanical rotation, and is determined by only the angular velocity of the rotation without any material parameters.

論文

Numerical study on influence of Ohnesorge number and Reynolds number on the jet breakup behavior using the lattice Boltzmann method

岩澤 譲*; 阿部 豊*; 金子 暁子*; 金川 哲也*; 齋藤 慎平*; 松尾 英治*; 海老原 健一; 坂場 弘*; 小山 和也*; 成合 英樹*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 7 Pages, 2015/05

高速炉の炉心溶融事故時における事故後冷却性評価のために、冷却材中にジェット状に射出された溶融燃料の微粒化挙動を詳細に把握することが望まれている。本研究では、粘性がジェット挙動に与える影響を調べるために、3次元二相流体格子ボルツマンモデルを用いたジェット挙動の数値シミュレーションを行い、結果をオーネゾルゲ数とレイノルズ数で整理した。結果として、ジェット挙動の評価には、ジェットの粘性と同様に冷却材の粘性の影響も考慮する必要があることを示した。

論文

Rotational Doppler effect and Barnett field in spinning NMR

中堂 博之; 針井 一哉; 松尾 衛; 家田 淳一; 小野 正雄; 前川 禎通; 齊藤 英治

Journal of the Physical Society of Japan, 84(4), p.043601_1 - 043601_4, 2015/04

 被引用回数:15 パーセンタイル:73.28(Physics, Multidisciplinary)

We report the observation of the rotational Doppler effect using nuclear magnetic resonance (NMR). We have developed a coil-spinning technique that enables measurements by rotating a detector and fixing a sample. We found that the rotational Doppler effect gives rise to NMR frequency shifts equal to the rotation frequency. We formulate the rotational Doppler effect and the Barnett field using a vector model for the nuclear magnetic moment. This formulation reveals that, with just the sample rotating, both effects cancel each other, thereby explaining the absence of an NMR frequency shift in conventional sample-spinning NMR measurements.

論文

格子ボルツマン法によるジェットブレイクアップ挙動解析

松尾 英治*; 阿部 豊*; 岩澤 譲*; 海老原 健一; 小山 和也*

日本機械学会論文集(インターネット), 81(822), p.14-00409_1 - 14-00409_20, 2015/02

ナトリウム冷却高速炉の炉心崩壊事故を想定した場合、溶融炉心材料の冷却材へのジェットのブレイクアップ挙動を理解することが必要であることから、流体力学的相互作用によるジェットブレイクアップ挙動を格子ボルツマン法(LBM)を用いシミュレーションした。まず、実験との比較により、LBMのジェットブレイクアップシミュレーションへの適用可能性を検証した。さらに、ウェーバー数及びフルード数などの無次元数の影響をLBMを使って調べた。その結果、ジェット界面が不安定になる場合、ジェットブレイクアップ長さはフルード数に依存せず、エプスタインの相関式とよく一致することが分かった。なお、本論文は、日本機械学会第18回動力・エネルギー技術シンポジウムでの発表内容を詳細にまとめたものである。

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