検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年
検索結果: 38 件中 1件目~20件目を表示

発表形式

Initialising ...

選択項目を絞り込む

掲載資料名

Initialising ...

発表会議名

Initialising ...

筆頭著者名

Initialising ...

キーワード

Initialising ...

使用言語

Initialising ...

発行年

Initialising ...

開催年

Initialising ...

選択した検索結果をダウンロード

論文

Ginzburg-Landau action and polarization current in an excitonic insulator model of electronic ferroelectricity

安立 裕人*; 池田 直*; 齊藤 英治

Physical Review B, 107(15), p.155142_1 - 155142_10, 2023/04

In comparison to transport of spin polarization in ferromagnets, transport of electric polarization in ferroelectrics remains less explored. Taking an excitonic insulator model of electronic ferroelectricity as a prototypical example, we theoretically investigate the low-energy dynamics and transport of electric polarization by microscopically constructing the Ginzburg-Landau action. We show that, because of the scalar nature of the excitonic order parameter, only the longitudinal fluctuations are relevant to the transport of electric polarization. We also formulate the electric-polarization diffusion equation, in which the electric-polarization current is defined purely electronically without recourse to the lattice degrees of freedom.

論文

Sodium-cooled Fast Reactors

大島 宏之; 森下 正樹*; 相澤 康介; 安藤 勝訓; 芦田 貴志; 近澤 佳隆; 堂田 哲広; 江沼 康弘; 江連 俊樹; 深野 義隆; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

ナトリウム冷却高速炉(SFR: Sodium-cooled Fast Reactor)の歴史や、利点、課題を踏まえた安全性、設計、運用、メンテナンスなどについて解説する。AIを利用した設計手法など、SFRの実用化に向けた設計や研究開発についても述べる。

論文

Purification of anionic fluorescent probes through precise fraction collection with a two-point detection system using multiple-stacking preparative capillary transient isotachophoresis

原賀 智子; 辻村 大翔*; 宮内 さおり*; 上村 拓也*; 渋川 雅美*; 齋藤 伸吾*

Electrophoresis, 41(13-14), p.1152 - 1159, 2020/07

 被引用回数:4 パーセンタイル:46.03(Biochemical Research Methods)

アクチノイド等の分析に必要な蛍光性試薬(陰イオン性蛍光プローブ)を高純度化するための技術を開発した。微小サンプルの分析に用いられるキャピラリー電気泳動法のうち、検出点を複数個所有する過渡的等速電気泳動法を開発し、キャピラリー中の泳動速度を泳動毎に正確に算出することにより、分取のタイミングを調整し、目的の成分のみを精確に分取する手法を確立した。これにより、分析に必要な試薬に含まれる不純物を除去し、95$$sim$$99%の高純度化に成功した。

論文

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.*; 辻 義之*; 國立 將真*; 久保 渉*; 鈴木 颯*; 富田 英生*; 鬼柳 善明*; 井口 哲夫*; 松下 琢*; 和田 信雄*; et al.

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

 被引用回数:0 パーセンタイル:0(Instruments & Instrumentation)

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer $$^{4}$$He$$_{2}$$$$^{ast}$$ are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + $$^{3}$$He $$rightarrow$$ $$^{3}$$T + p. This reaction is induced by neutron irradiation of the $$^{3}$$He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (J-PARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These $$^{4}$$He$$_{2}$$$$^{ast}$$ clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the $$^{4}$$He$$_{2}$$$$^{ast}$$ clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium.

論文

Generation of $$^{4}$$He$$_2^{*}$$ clusters via neutron-$$^{3}$$He absorption reaction toward visualization of full velocity field in quantum turbulence

松下 琢*; Sonnenschein, V.*; Guo, W.*; 林田 洋寿*; 廣井 孝介; 広田 克也*; 井口 哲夫*; 伊藤 大介*; 北口 雅暁*; 鬼柳 善明*; et al.

Journal of Low Temperature Physics, 196(1-2), p.275 - 282, 2019/07

For flow visualization study of quantum turbulence in superfluid $$^{4}$$He, $$^{4}$$He$$_2^{*}$$ excimers are unique tracers which follow only normal-fluid component flow above 1 K. To generate detectable small $$^{4}$$He$$_2^{*}$$ clouds (clusters) required for full-space velocity field measurements, we have adopted a new method based on neutron absorption reaction of $$^{3}$$He impurities in $$^{4}$$He and conducted proof-of-principle experiments. Generation of the $$^{4}$$He$$_2^{*}$$ excimers was detected by laser-induced fluorescence using photomultiplier tubes. The fluorescence was observed to increase proportionally to the neutron flux, suggesting that a sufficient amount of $$^{4}$$He$$_2^{*}$$ excimers were generated by neutrons. We also estimated the number of $$^{4}$$He$$_2^{*}$$ excimers possibly generated by $$gamma$$-rays and found that the relevant contribution was less than 40%. Thus, the majority of the $$^{4}$$He$$_2^{*}$$ excimers was confirmed to be generated via n-$$^{3}$$He absorption reactions.

論文

Experimental observation of temperature and magnetic-field evolution of the 4${it f}$ states in CeFe$$_{2}$$ revealed by soft X-ray magnetic circular dichroism

斎藤 祐児; 保井 晃*; 渕本 寛人*; 中谷 泰博*; 藤原 秀紀*; 今田 真*; 鳴海 康雄*; 金道 浩一*; 高橋 稔*; 海老原 孝雄*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

 被引用回数:2 パーセンタイル:17.22(Materials Science, Multidisciplinary)

単結晶CeFe$$_2$$を用い、X線吸収(XAS)磁気円2色性(XMCD)の高精度実験により、その強磁性的秩序相におけるCe4$$f$$状態を調べた。Ce $$M_{4,5}$$ XMCDスペクトルは、温度及び磁場に依存した形状変化を示す一方、Ce $$M_{4,5}$$ XAS、Fe $$L_{2,3}$$ XAS及びXMCDスペクトルでは変化が観測されないという通常の強磁性体とは異なる現象が観測された。このような振る舞いは、Ce 4$$f^1$$配置の$$J=5/2$$基底状態と$$J=7/2$$状態が混ざり合ったことに由来すると解釈できる。外部摂動に対し非常に敏感なCe 4$$f$$状態は、本物質での強磁性相と反強磁相が隣接する磁気不安定性と関連付けることができる。我々の実験データは、混成の強い強磁性Ce化合物の物性に対して、貴重な情報を与える。

論文

平成28年度技術士試験「原子力・放射線部門」対策講座; 平成27年度技術士一次試験「原子力・放射線部門」; 専門科目の解説

高橋 直樹; 鈴木 惣十; 齋藤 拓人; 上野 隆; 阿部 定好; 山中 淳至; 谷川 聖史; 中村 大司; 佐々木 俊一; 峯 忠治

日本原子力学会ホームページ(インターネット), 20 Pages, 2017/05

本資料は、平成28年度技術士試験(原子力・放射線部門)一次試験受験を志す者への学習支援を目的とし、平成27年度に実施された技術士試験(原子力・放射線部門)一次試験の出題傾向分析や学習方法等についての全体解説、専門科目の解答と解説を行うものである。なお、本資料は技術士制度の普及と技術士育成を目的とした日本原子力学会から日本技術士会(原子力・放射線部会)への依頼に基づき、原子力機構所属の技術士等が作成を行ったものである。

論文

Electronic structures of ferromagnetic CeAgSb$$_{2}$$; Soft X-ray absorption, magnetic circular dichroism, and angle-resolved photoemission spectroscopies

斎藤 祐児; 藤原 秀紀*; 山口 貴司*; 中谷 泰博*; 森 健雄*; 渕本 寛人*; 木須 孝幸*; 保井 晃*; 宮脇 淳*; 今田 真*; et al.

Journal of the Physical Society of Japan, 85(11), p.114713_1 - 114713_7, 2016/11

 被引用回数:13 パーセンタイル:68.29(Physics, Multidisciplinary)

軟X線吸収(XAS)、磁気円二色性(XMCD)、角度分解光電子分光(ARPES)により強磁性体CeAgSb$$_{2}$$の電子状態を調べた。Ce $$M_{4,5}$$ XASスペクトルのサテライト構造の強度が非常に小さいことから、Ce 4${it f}$電子は非常に局在的であることが明らかとなった。Ce $$M_{4,5}$$ XASの線二色性効果から、Ce 4${it f}$基底状態は${it c}$軸方向を向いた$$Gamma$$$$_{6}$$であることが分かった。XMCD結果は、CeAgSb$$_{2}$$の局在磁性描像を支持する。さらに、ARPESで得られたバンド構造は、CeAgSb$$_{2}$$では無くLaAgSb$$_{2}$$に対するバンド計算結果とよく一致する。しかしながら、Ce 3${it d}$-4${it f}$共鳴ARPES結果では、ブリルアンゾーンの一部でCe 4$$f^{1}_{5/2}$$と4$$f^{1}_{7/2}$$ピーク強度比に波数依存性が観測され、Ce 4${it f}$と伝導電子に無視できない混成効果が有ることが分かった。このことは、CeAgSb$$_{2}$$のあまり大きくない電子比熱係数と関係づけることができる。

論文

Thermoelectric generation based on spin Seebeck effects

内田 健一*; 安立 裕人; 吉川 貴史*; 桐原 明宏*; 石田 真彦*; 萬 伸一*; 前川 禎通; 齊藤 英治*

Proceedings of the IEEE, 104(10), p.1946 - 1973, 2016/10

 被引用回数:205 パーセンタイル:99.2(Engineering, Electrical & Electronic)

The spin Seebeck effect (SSE) refers to the generation of a spin current as a result of a temperature gradient in magnetic materials including insulators. The SSE is applicable to thermoelectric generation because the thermally generated spin current can be converted into a charge current via spin-orbit interaction in conductive materials adjacent to the magnets. The insulator-based SSE device exhibits unconventional characteristics potentially useful for thermoelectric applications, such as simple structure, device-design exibility, and convenient scaling capability. In this article, we review recent studies on the SSE from the viewpoint of thermoelectric applications.

論文

Origin of the spin Seebeck effect in compensated ferrimagnets

Gepr$"a$gs, S.*; Kehlberger, A.*; Coletta, F.*; Qiu, Z.*; Guo, E.-J.*; Schulz, T.*; Mix, C.*; Meyer, S.*; Kamra, A.*; Althammer, M.*; et al.

Nature Communications (Internet), 7, p.10452_1 - 10452_6, 2016/02

 被引用回数:137 パーセンタイル:97.31(Multidisciplinary Sciences)

Magnons are the elementary excitations of a magnetically ordered system. Here, we show that the spin Seebeck effect is sensitive to the complexities of the magnon spectrum. The spin Seebeck effect is caused by a thermally excited spin dynamics that is converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the spin Seebeck effect in the ferrimagnet gadlinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that high-energy exchange magnons play a key role in the spin Seebeck effect.

論文

平成28年度技術士試験「原子力・放射線部門」対策講座; 平成27年度技術士二次試験「原子力・放射線部門」; そのポイントを探る$$sim$$全体解説、必須科目及び選択科目の設問と解説

高橋 直樹; 芳中 一行; 原田 晃男; 山中 淳至; 上野 隆; 栗原 良一; 鈴木 惣十; 高松 操; 前田 茂貴; 井関 淳; et al.

日本原子力学会ホームページ(インターネット), 64 Pages, 2016/00

本資料は、平成28年度技術士試験(原子力・放射線部門)の受験を志す者への学習支援を目的とし、平成27年度技術士試験(原子力・放射線部門)の出題傾向分析や学習方法等についての全体解説、必須科目の解答と解説及び選択科目の模範解答や解答作成にあたってのポイント解説を行うものである。なお、本資料は技術士制度の普及と技術士育成を目的とした日本原子力学会から日本技術士会(原子力・放射線部会)への依頼に基づき、原子力機構所属の技術士及び社内外の各分野における専門家により作成を行ったものである。

論文

Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers

Ramos, R.*; 吉川 貴史*; Aguirre, M.*; Lucas, I.*; Anad$'o$n, A.*; 小宅 教文*; 内田 健一*; 安立 裕人; 塩見 淳一郎*; Algarabel, P. A.*; et al.

Physical Review B, 92(22), p.220407_1 - 220407_5, 2015/12

 被引用回数:65 パーセンタイル:90.95(Materials Science, Multidisciplinary)

Spin Seebeck effects have been investigated in highly crystalline magnetic multilayer films. Voltage as well as power generated by the spin Seebeck effect were found to be significantly enhanced with increasing the number of layers, $$n$$. This voltage enhancement defies the simple understanding of the spin Seebeck effect and suggests that spin current flowing between the magnetic layers in the thickness direction plays an important role in the multilayer SSE systems and the observed voltage enhancement.

論文

Magnon instability driven by heat current in magnetic bilayers

大沼 悠一*; 安立 裕人; 齊藤 英治; 前川 禎通

Physical Review B, 92(22), p.224404_1 - 224404_8, 2015/12

 被引用回数:8 パーセンタイル:35.75(Materials Science, Multidisciplinary)

We theoretically demonstrate that in a ferromagnet/paramagnet bilayer, a magnon instability accompanied by a gigahertz microwave emission can be driven simply by means of a temperature bias. Employing many-body theory for investigating the effects of a phonon heat current on the magnon lifetime, we show that the magnon instability occurs upon the suppression of the umklapp scattering at low temperatures, leading to microwave emission. The present finding provides crucial information about the interplay of spin current and heat current.

論文

Generation of spin currents by surface plasmon resonance

内田 健一*; 安立 裕人; 菊池 大介*; 伊藤 俊*; Qiu, Z.*; 前川 禎通; 齊藤 英治

Nature Communications (Internet), 6, p.5910_1 - 5910_8, 2015/01

 被引用回数:46 パーセンタイル:85.43(Multidisciplinary Sciences)

Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light; electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ interface.

論文

Enhanced dc spin pumping into a fluctuating ferromagnet near Tc

大沼 悠一*; 安立 裕人; 齊藤 英治; 前川 禎通

Physical Review B, 89(17), p.174417_1 - 174417_10, 2014/05

 被引用回数:91 パーセンタイル:94.31(Materials Science, Multidisciplinary)

A linear-response formulation of the dc spin pumping, i.e., a spin injection from a precessing ferromagnet into an adjacent spin sink, is developed in view of describing many-body effects caused by spin fluctuations in the spin sink. It is shown that, when an itinerant ferromagnet near Tc is used as the spin sink, the spin pumping is largely increased owing to the fluctuation enhancement of the spin conductance across the precessing ferromagnet/spin sink inerface. As an example, the enhanced spin pumping from yttrium iron garnet into nickel palladium alloy is analyzed by means of a self-consistent renormalization scheme, and it is predicted that the enhancement can be as large as tenfold.

論文

Separation of longitudinal spin Seebeck effect from anomalous Nernst effect; Determination of origin of transverse thermoelectric voltage in metal/insulator junctions

吉川 貴史*; 内田 健一*; 大門 俊介*; 塩見 雄毅*; 安立 裕人; Qiu, Z.*; Hou, D.*; Jin, X.-F.*; 前川 禎通; 齊藤 英治

Physical Review B, 88(21), p.214403_1 - 214403_11, 2013/12

 被引用回数:120 パーセンタイル:96.14(Materials Science, Multidisciplinary)

The longitudinal spin Seebeck effect and the anomalous Nernst effect are investigated in various metal/insulator junction systems, and the clear separation of the longitudinal spin Seebeck effect from the anomalous Nernst effect induced by static magnetic proximity is demonstrated. It is shown that, in Pt/Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$ samples, the longitudinal spin Seebeck effect is three orders of magnitude greater than the proximity-driven anomalous Nernst effect.

論文

Spin-wave spin current in magnetic insulators

内田 健一*; 安立 裕人; 梶原 瑛祐*; 前川 禎通; 齊藤 英治

Solid State Physics, 64; Recent Advances in Magnetic Insulators; From Spintronics to Microwave Applications, p.1 - 27, 2013/11

 被引用回数:11 パーセンタイル:15.33(Physics, Condensed Matter)

A spin wave is a collective motion of magnetic moment in magnetically ordered materials. Although spin waves have been known and investigated for many years, resent research has revealed that the spin wave plays an important role in spintronics as a carrier of spin current, i.e., a flow of spin angular momentum. Such a spin-wave spin current is available in magnetic insulators even in the absence of conduction electrons, thus opens a new route for investigating spintronic phenomena in magnetic insulators. In this article we review recent progress in insulator spintronics.

論文

Spin current; Experimental and theoretical aspects

前川 禎通; 安立 裕人; 内田 健一*; 家田 淳一; 齊藤 英治

Journal of the Physical Society of Japan, 82(10), p.102002_1 - 102002_23, 2013/10

 被引用回数:84 パーセンタイル:78.4(Physics, Multidisciplinary)

The flow of electron spin, the so-called "spin current", is a key concept in the recent progress in spintronics. When the spin current interacts with the magnetic moment in a ferromagnetic metal, the angular momentum and energy conservations give rise to the spin transfer torque and spin-motive force, respectively. When it is injected into a non-magnetic metal attached to a ferromagnet, the electric current is induced through the spin-charge conversion mechanism (inverse spin Hall effect). The generation and manipulation of the spin current and a variety of novel phenomena given by the spin current, including the spin Seebeck effect and spin-motive force, are discussed.

論文

Unidirectional spin-wave heat conveyer

安 東秀*; Vasyuchka, V. I.*; 内田 健一*; Chumak, A. V.*; 山口 和也*; 針井 一哉; 大江 純一郎*; Jungfleisch, M. B.*; 梶原 瑛祐*; 安立 裕人; et al.

Nature Materials, 12(6), p.549 - 553, 2013/06

 被引用回数:122 パーセンタイル:96.36(Chemistry, Physical)

In this paper, we show a magnetically controllable heat flow caused by a spin-wave current. The direction of the flow can be switched by applying a magnetic field. When microwave energy is applied to a region of ferrimagnetic Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$, an end of the magnet far from this region is found to be heated in a controlled manner and a negative temperature gradient towards it is formed. This is due to unidirectional energy transfer by the excitation of spin-wave modes without time-reversal symmetry and to the conversion of spin waves into heat. The magnetically controlled remote heating we observe is directly applicable to the fabrication of a heat-flow controller.

論文

Theory of the spin Seebeck effect

安立 裕人; 内田 健一*; 齊藤 英治; 前川 禎通

Reports on Progress in Physics, 76(3), p.036501_1 - 036501_20, 2013/03

 被引用回数:336 パーセンタイル:96.24(Physics, Multidisciplinary)

スピンゼーベック効果とは強磁性体内の温度勾配によってスピン圧を生成する現象であり、この生成されたスピン圧は強磁性体に接着した非磁性金属内に巨視的な長さスケールのスピン注入を可能にする。スピンホール効果はこのスピン流を横方向の電圧に変換することが可能であるため、よく知られた熱電効果のように熱起電力を生成することが可能である。近年の理論及び実験の進歩はスピンゼーベック効果におけるフォノンとマグノンの重要性を明らかにしてきた。スピンゼーベック効果の理論を解説するとともに、他の熱スピン現象についても簡単な紹介を行う。

38 件中 1件目~20件目を表示