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論文

Neutron transmission CB-KID imager using samples placed at room temperature

石田 武和*; Vu, TheDang*; 宍戸 寛明*; 相澤 一也; 奥 隆之; 及川 健一; 原田 正英; 小嶋 健児*; 宮嶋 茂之*; 小山 富男*; et al.

Journal of Low Temperature Physics, 214(3-4), p.152 - 157, 2024/02

We built a new cryostat to apply a current-biased kinetic inductance detector (CB-KID) for conducting neutron transmission imaging of room temperature samples under pulsed neutrons. A Wood's metal alloy of melting temperature 75.2$$^{circ}$$C was placed at room temperature to inspect the measurement system at J-PARC. Since one of the four phases of Wood's metal is a fine Cd-rich needle phase (width $$sim$$ 25 $$mu$$m and length $$sim$$ 5 mm), it is suitable for observing fine mosaic structure selectively by neutron imaging. The spatial resolution of the CB-KID imager was estimated as $$sim$$ 10 $$mu$$m by using a Gd Siemens-star pattern. The CB-KID system is useful to conduct transmission imaging for various materials rather easily at room temperature.

報告書

核燃料再処理施設におけるグローブボックス用グローブの物性調査; 定期交換したグローブの物性と使用可能年数の推測

山本 昌彦; 西田 直樹; 小林 大輔; 根本 良*; 林 宏幸*; 北尾 貴彦; 久野 剛彦

JAEA-Technology 2023-004, 30 Pages, 2023/06

JAEA-Technology-2023-004.pdf:1.94MB

日本原子力研究開発機構の東海再処理施設において核燃料物質の取り扱いに使用するグローブボックス用グローブ(以下、「グローブ」という。)は、内部規則にて使用期限が定められており、グローブボックスに取り付け後、異常の有無に係わらず最長4年で交換している。一方、グローブの材質は合成ゴムであることから、使用環境(使用頻度、薬品、放射線量等)によってその劣化度合は異なる。そこで、本件では使用環境毎にグローブを分類し、その物性値を測定すること等により、グローブの劣化状況に応じた使用可能年数の技術的評価手法を確立するとともに、グローブの使用可能な年数を推測した。外観上の異常もなく定期交換したグローブについて、測定した物性値は、新品のグローブの納品時に確認している受入基準値を満足し、新品のグローブと同等の物理的特性を有していることが分かった。このため、使用期限を迎えたこれらグローブは、新品のグローブの最長使用年数である4年を追加した合計8年間の使用が可能であると考えられた。また、グローブの物性値と使用年数をプロットして外挿線を作成した結果、使用年数8年における物性値は、過去にグローブの破損等が報告されている物性値よりも安全側の値を示し、非管理区域の倉庫にて8年及び23年間保管した長期保管グローブの物性値と有意な差は見られなかった。これらより、東海再処理施設におけるグローブの最長使用年数は8年と設定した。なお、グローブの点検頻度、項目は従来の実施内容から変更せず、異常が確認されれば使用年数に関係なく速やかに交換される管理であることから、使用年数を8年に延長した場合でもグローブ使用に伴う安全性の低下(リスクの上昇)は生じない。また、使用年数の延長に伴い、グローブの購入費、グローブ交換等の作業労力、廃棄物発生量を従来よりもそれぞれ約4割低減させることができ、定期のグローブ交換に伴う汚染発生のリスク、作業者の被ばくのリスクも低減され、グローブ管理の効率化・合理化が図られた。

論文

The Damage analysis for irradiation tolerant spin-driven thermoelectric device based on single-crystalline Y$$_3$$Fe$$_5$$O$$_{12}$$/Pt heterostructures

家田 淳一; 岡安 悟; 針井 一哉*; 小畠 雅明; 吉井 賢資; 福田 竜生; 石田 真彦*; 齊藤 英治

IEEE Transactions on Magnetics, 58(8), p.1301106_1 - 1301106_6, 2022/08

 被引用回数:1 パーセンタイル:24.36(Engineering, Electrical & Electronic)

スピンゼーベック効果(SSE)に基づくスピン駆動熱電(STE)デバイスと、熱源としての放射性同位元素の組み合わせは、宇宙探査機の電源などの応用における次世代の発電方法としての可能性を秘めている。しかし、スピン熱電デバイスの照射耐性を示す利用可能な知識は非常に限られている。重イオンビーム加速器と硬X線光電子分光法(HAXPES)測定を使用した分析を通じて、Y$$_3$$Fe$$_5$$O$$_{12}$$/Ptヘテロ構造に基づく典型的なSTEデバイスが高エネルギー重イオンビームの照射に対する耐性を持つことを検証する。使用済み核燃料の表面から放出される核分裂生成物による累積損傷をモデル化した320MeVの金イオンビームを使用し、線量レベルを変えることにより、SSE要素の熱電および磁気特性が$$10^{10}$$イオン/cm$$^2$$フルエンスまでのイオン照射線量の影響を受けず、イオントラックがサンプル表面をほぼ完全に覆う約$$10^{12}$$イオン/cm$$^2$$でSSE信号が消滅することを確認した。さらに、HAXPES測定は、Y$$_3$$Fe$$_5$$O$$_{12}$$/Pt界面への影響を理解するために実行した。HAXPES測定は、SSE信号を減少させる化学反応が照射線量の増加とともに強化されることを示唆している。過酷な環境使用に適用できるより優れたSTEデバイスを開発するために、Y$$_3$$Fe$$_5$$O$$_{12}$$/Ptで損傷分析の現在の理解を共有したい。

論文

グローブボックス用グローブの物性調査と使用可能年数の推測

小林 大輔; 山本 昌彦; 西田 直樹; 三好 竜太; 根本 良*; 林 宏幸*; 加藤 圭将; 西野 紗樹; 久野 剛彦; 北尾 貴彦; et al.

日本保全学会第18回学術講演会要旨集, p.237 - 240, 2022/07

東海再処理施設のグローブボックスに取付けられているグローブは、一律に使用期限を定めて定期的に交換している。ゴム製品であるグローブは、使用環境(使用頻度,化学薬品,放射線等)により、劣化度合いが異なることが外観上からも推察される。本件では、様々な使用環境下で定期交換したグローブの物性値(引張強さ,伸び率,硬さ)を測定し、新品グローブの物性値との比較により、劣化の程度並びに使用可能年数を推定した。その結果、外観に異常の無いグローブは、新品グローブの受入基準値以上の物性値であることが分かった。また、外挿した物性値からはこれまで報告されたグローブ損傷時の物性値よりも十分に大きいことから、外観に異常が無く定期的に交換するグローブの物性に劣化は見られず、グローブの使用可能年数は8年と推測された。

論文

Practical tests of neutron transmission imaging with a superconducting kinetic-inductance sensor

Vu, TheDang; 宍戸 寛明*; 相澤 一也; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 奥 隆之; 曽山 和彦; 宮嶋 茂之*; et al.

Nuclear Instruments and Methods in Physics Research A, 1006, p.165411_1 - 165411_8, 2021/08

 被引用回数:0 パーセンタイル:0.02(Instruments & Instrumentation)

We found that the sizes of the Gd islands determined from the transmission image correlated strongly with those determined from the SEM image. We demonstrated the CB-KID could be used to identify (1) tiny voids in a thermally sprayed continuous Gd$$_2$$O$$_3$$ film in and (2) various mosaic morphologies and different eutectic microstructures in Wood's metal samples. The fact that the CB-KID system could be used to identify features of samples with a wide distribution of sizes and thicknesses is promising for real application of the device for imaging samples of interest to material scientists. Operating the CB-KID at higher temperatures appreciably improved the efficiency for simultaneously identifying the X and Y positions of hotspots. We also compared the detection efficiency with the PHITS simulations. We now plan to improve the detection efficiency by increasing the thickness of the $$^{10}$$B neutron conversion layer

論文

Analysis of residual stress in steel bar processed by cold drawing and straightening

西田 智*; 西野 創一郎*; 関根 雅彦*; 岡 勇希*; Harjo, S.; 川崎 卓郎; 鈴木 裕士; 森井 幸生*; 石井 慶信*

Materials Transactions, 62(5), p.667 - 674, 2021/05

 被引用回数:2 パーセンタイル:35.36(Materials Science, Multidisciplinary)

In this study, we used neutron diffraction to analyze in a non-destructive method the distribution of internal residual stress in a free-cutting steel bar processed by cold drawing and straightening. The residual stresses were successfully measured with excellent stress balance. The residual stresses generated by the cold-drawing process were reduced by subsequent straightening, and the distribution of residual stresses by finite element method (FEM) simulation was consistent with the measured values by neutron diffraction. As a result of the FEM analysis, it is assumed that the rod was subjected to strong tensile strains in the axial direction during the drawing process, and the residual stresses were generated when the rod was unloaded. Those residual stresses were presumably reduced by the redistribution of residual stresses in the subsequent straightening process.

論文

Homogeneity of neutron transmission imaging over a large sensitive area with a four-channel superconducting detector

Vu, TheDang; 宍戸 寛明*; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 宮嶋 茂之*; 奥 隆之; 曽山 和彦; 相澤 一也; et al.

Superconductor Science and Technology, 34(1), p.015010_1 - 015010_10, 2021/01

 被引用回数:3 パーセンタイル:28.82(Physics, Applied)

We demonstrated that a four-readout superconducting neutron imaging system shows good spatial heterogeneity and linearity using the delay-line method. We examined the precise pattern of a $$^{10}$$B-dot-array absorber and found the X-direction pitch (Px) = 250.7 um with a scatter of (Hx)= 5.4 um and the Y-direction pitch (Py)= 249.1 um with a scatter of (Hy)= 3.4 um while the $$^{10}$$B dot array was fully extended toward the X direction across the detector sensitive area. We consider that this demonstrates detection with good spatial homogeneity and conclude. The transmission-imaging system is suitable for use at pulsed neutron facilities. We also reported a clear transmission image of tiny screws and nuts, and ladybug (insect). We recognize that further efforts to improve the detection efficiency are necessary to make using the detector more practical.

論文

Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions

岡安 悟; 針井 一哉*; 小畠 雅明; 吉井 賢資; 福田 竜生; 石田 真彦*; 家田 淳一; 齊藤 英治

Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08

AA2020-0071.pdf:0.69MB

 被引用回数:3 パーセンタイル:20(Physics, Applied)

The ion-irradiation tolerance of thermoelectric devices based on the spin Seebeck effect (SSE) was investigated by using 320 MeV gold ion (Au$$^{24+}$$) beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. For this purpose, prototypical Pt/Y$$_3$$Fe$$_5$$O$$_{12}$$/Gd$$_3$$Ga$$_5$$O$$_{12}$$ SSE elements were irradiated with varying the dose level at room temperature and measured the SSE voltage of them. We confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation up to $$10^{10}$$ ions/cm$$^2$$ fluence and that the SSE signal is extinguished around $$10^{12}$$ ions/cm$$^2$$, in which the ion tracks almost fully cover the sample surface. We also performed the hard X-ray photoemission spectroscopy (HAXPES) measurements to understand the effects at the interface of Pt/Y$$_3$$Fe$$_5$$O$$_{12}$$. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. The present study demonstrates that SSE-based devices are applicable to thermoelectric generation even in harsh environments for a long time period.

論文

Kinetic inductance neutron detector operated at near critical temperature

Vu, TheDang; 西村 和真*; 宍戸 寛明*; 原田 正英; 及川 健一; 宮嶋 茂之*; 日高 睦夫*; 奥 隆之; 曽山 和彦; 相澤 一也; et al.

Journal of Physics; Conference Series, 1590, p.012036_1 - 012036_9, 2020/07

 被引用回数:0 パーセンタイル:0.01

Our CB-KID neutron imager detects high spatial resolution neutrons transmission images by using a delay-line technique. We found that the number of events was remarkably increased with increasing the detector temperature until close to the critical temperature Tc. We investigated the properties of CB-KID at near Tc. We observed systematic changes of neutron signals as a function of the detector temperature from 4 K to Tc. The simulations modeled the sequential physical processes for $$^{10}$$B(n,$$alpha$$)$$^{7}$$Li reactions and energy deposition by particles within CB-KID, including neutrons, $$^{4}$$He particles, $$^{7}$$Li particles, photon and electron transport.

論文

Monte Carlo radiation transport modelling of the current-biased kinetic inductance detector

Malins, A.; 町田 昌彦; Vu, TheDang; 相澤 一也; 石田 武和*

Nuclear Instruments and Methods in Physics Research A, 953, p.163130_1 - 163130_7, 2020/02

AA2019-0261.pdf:0.84MB

 被引用回数:6 パーセンタイル:61.45(Instruments & Instrumentation)

Radiation transport simulations were used to analyse neutron imaging with the current-biased kinetic inductance detector (CB-KID). The PHITS Monte Carlo code was applied for simulating neutron, $$^{4}$$He, $$^{7}$$Li, photon and electron transport, $$^{10}$$B(n,$$alpha$$)$$^{7}$$Li reactions, and energy deposition by particles within CB-KID. Slight blurring in simulated CB-KID images originated $$^{4}$$He and $$^{7}$$Li ions spreading out in random directions from the $$^{10}$$B conversion layer in the detector prior to causing signals in the $$X$$ and $$Y$$ superconducting Nb nanowire meander lines. 478 keV prompt gamma rays emitted by $$^{7}$$Li nuclei from neutron-$$^{10}$$B reactions had negligible contribution to the simulated CB-KID images. Simulated neutron images of $$^{10}$$B dot arrays indicate that sub 10 $$mu$$m resolution imaging should be feasible with the current CB-KID design. The effect of the geometrical structure of CB-KID on the intrinsic detection efficiency was calculated from the simulations. An analytical equation was then developed to approximate this contribution to the detection efficiency. Detection efficiencies calculated in this study are upper bounds for the reality as the effects of detector temperature, the bias current, signal processing and dead-time losses were not taken into account. The modelling strategies employed in this study could be used to evaluate modifications to the CB-KID design prior to actual fabrication and testing, conveying a time and cost saving.

論文

Identification of advanced spin-driven thermoelectric materials via interpretable machine learning

岩崎 悠真*; 澤田 亮人*; Stanev, V.*; 石田 真彦*; 桐原 明宏*; 大森 康智*; 染谷 浩子*; 竹内 一郎*; 齊藤 英治; 萬 伸一*

npj Computational Materials (Internet), 5, p.103_1 - 103_6, 2019/10

 被引用回数:38 パーセンタイル:87.44(Chemistry, Physical)

Machine learning is becoming a valuable tool for scientific discovery. Particularly attractive is the application of machine learning methods to the field of materials development, which enables innovations by discovering new and better functional materials. To apply machine learning to actual materials development, close collaboration between scientists and machine learning tools is necessary. However, such collaboration has been so far impeded by the black box nature of many machine learning algorithms. It is often difficult for scientists to interpret the data-driven models from the viewpoint of material science and physics. Here, we demonstrate the development of spin-driven thermoelectric materials with anomalous Nernst effect by using an interpretable machine learning method called factorized asymptotic Bayesian inference hierarchical mixture of experts (FAB/HMEs). Based on prior knowledge of material science and physics, we were able to extract from the interpretable machine learning some surprising correlations and new knowledge about spin-driven thermoelectric materials. Guided by this, we carried out an actual material synthesis that led to the identification of a novel spin-driven thermoelectric material. This material shows the largest thermopower to date.

論文

Machine-learning guided discovery of a new thermoelectric material

岩崎 悠真*; 竹内 一郎*; Stanev, V.*; Gilad Kusne, A.*; 石田 真彦*; 桐原 明宏*; 井原 和紀*; 澤田 亮人*; 寺島 浩一*; 染谷 浩子*; et al.

Scientific Reports (Internet), 9, p.2751_1 - 2751_7, 2019/02

 被引用回数:50 パーセンタイル:93.23(Multidisciplinary Sciences)

Thermoelectric technologies are becoming indispensable in the quest for a sustainable future. Recently, an emerging phenomenon, the spin-driven thermoelectric effect (STE), has garnered much attention as a promising path towards low cost and versatile thermoelectric technology with easily scalable manufacturing. However, progress in development of STE devices is hindered by the lack of understanding of the fundamental physics and materials properties responsible for the effect. In such nascent scientific field, data-driven approaches relying on statistics and machine learning, instead of more traditional modeling methods, can exhibit their full potential. Here, we use machine learning modeling to establish the key physical parameters controlling STE. Guided by the models, we have carried out actual material synthesis which led to the identification of a novel STE material with a thermopower an order of magnitude larger than that of the current generation of STE devices.

論文

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; 阿部 充志*; 青木 正治*; Choi, S.*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

 被引用回数:13 パーセンタイル:99.28

High precision measurements of the ground state hyperfine structure (HFS) of muonium is a stringent tool for testing bound-state quantum electrodynamics (QED) theory, determining fundamental constants of the muon magnetic moment and mass, and searches for new physics. Muonium is the most suitable system to test QED because both theoretical and experimental values can be precisely determined. Previous measurements were performed decades ago at LAMPF with uncertainties mostly dominated by statistical errors. At the J-PARC Muon Science Facility (MUSE), the MuSEUM collaboration is planning complementary measurements of muonium HFS both at zero and high magnetic field. The new high-intensity muon beam that will soon be available at H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation for high-field measurements, and the latest results at zero field are presented.

論文

New precise measurement of muonium hyperfine structure interval at J-PARC

上野 恭裕*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; 伊藤 孝; 岩崎 雅彦*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

 被引用回数:3 パーセンタイル:86.59

MuSEUM is an international collaboration aiming at a new precise measurement of the muonium hyperfine structure at J-PARC (Japan Proton Accelerator Research Complex). Utilizing its intense pulsed muon beam, we expect a ten-fold improvement for both measurements at high magnetic field and zero magnetic field. We have developed a sophisticated monitoring system, including a beam profile monitor to measure the 3D distribution of muonium atoms to suppress the systematic uncertainty.

論文

Gamma radiation resistance of spin Seebeck devices

Yagmur, A.*; 内田 健一*; 井原 和紀*; 井岡 郁夫; 吉川 貴史*; 小野 円佳*; 遠藤 純一*; 柏木 王明*; 中島 哲也*; 桐原 明宏*; et al.

Applied Physics Letters, 109(24), p.243902_1 - 243902_4, 2016/12

 被引用回数:3 パーセンタイル:15.07(Physics, Applied)

スピンゼーベック効果(SSE)に基づく熱電素子の$$gamma$$線抵抗性を調べるため、約3$$times$$10$$^{5}$$Gyの$$gamma$$線照射試験を実施した。SSE素子には、Pt/Ni$$_{0.2}$$Zn$$_{0.3}$$Fe$$_{2.5}$$O$$_{4}$$/GlassとPt/Bi$$_{0.1}$$Y$$_{2.9}$$Fe$$_{5}$$O$$_{12}$$/Gd$$_{3}$$Ga$$_{5}$$O$$_{12}$$を用いた。SSE素子の熱電特性,磁気特性、構造は、$$gamma$$線照射により影響されないことを確認した。この結果は、SSE素子が厳しい照射環境でさえ熱電素子として適用可能なことを示した。

論文

New muonium HFS measurements at J-PARC/MUSE

Strasser, P.*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 勝彦*; 伊藤 孝; 岩崎 雅彦*; et al.

Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12

 被引用回数:7 パーセンタイル:91.29

At the Muon Science Facility (MUSE) of J-PARC (Japan Proton Accelerator Research Complex), the MuSEUM collaboration is planning new measurements of the ground state hyperfine structure (HFS) of muonium both at zero field and at high magnetic field. The previous measurements were performed both at LAMPF (Los Alamos Meson Physics Facility) with experimental uncertainties mostly dominated by statistical errors. The new high intensity muon beam that will soon be available at MUSE H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation, and the results of a first commissioning test experiment at zero field are presented.

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

Flexible heat-flow sensing sheets based on the longitudinal spin Seebeck effect using one-dimensional spin-current conducting films

桐原 明宏*; 近藤 幸一*; 石田 真彦*; 井原 和紀*; 岩崎 悠真*; 染谷 浩子*; 松葉 明日華*; 内田 健一*; 齊藤 英治; 山本 直治*; et al.

Scientific Reports (Internet), 6, p.23114_1 - 23114_7, 2016/03

 被引用回数:60 パーセンタイル:90.81(Multidisciplinary Sciences)

ヒートフローセンシングは、将来的にスマート熱管理の重要な技術要素となることが期待されている。従来、ゼーベック効果に基づく熱電変換技術は、熱の流れを電圧に変換することによって熱流を測定するために使用されてきた。しかし、ユビキタス・ヒートフロー可視化のためには、非常に低い熱抵抗を有する薄く柔軟なセンサが非常に望まれている。近年、別のタイプの熱電効果である縦スピンゼーベック効果が大きな関心を集めている。これは縦スピンゼーベック効果が、単純な薄膜デバイス構造のような熱電アプリケーションにとって有利な機能を潜在的に提供するためである。ここでは、縦スピンゼーベック効果ベースのフレキシブル熱電シートを紹介する。このシートは、熱流検出の用途に特に適している。この熱電シートは、「フェライトめっき」として知られているスプレーコーティング法を用いてフレキシブルプラスチックシート上に形成されたNi$$_{0.2}$$Zn$$_{0.3}$$Fe$$_{2.5}$$O$$_4$$フィルムを含んでいる。実験結果は、膜面に垂直に配向した柱状結晶構造を有するフェライトめっき膜が、曲げ可能な縦スピンゼーベック効果ベースのセンサに適した独特の一次元スピン流導体として機能することを示唆している。この新しく開発された薄い熱電シートは、熱流の本来の流れを妨げることなく、さまざまな形の熱源に取り付けられ、多目的な熱流の測定と管理につながる。

論文

Enhancement of spin-Seebeck effect by inserting ultra-thin Fe$$_{70}$$Cu$$_{30}$$ interlayer

菊池 大介*; 石田 真彦*; 内田 健一*; Qiu, Z.*; Murakami, T.*; 齊藤 英治

Applied Physics Letters, 106(8), p.082401_1 - 082401_4, 2015/02

 被引用回数:28 パーセンタイル:74.8(Physics, Applied)

We report the longitudinal spin-Seebeck effects (LSSEs) for Pt/Fe$$_{70}$$Cu$$_{30}$$/BiY$$_{2}$$Fe$$_{5}$$O$$_{12}$$ (BiYIG) and Pt/BiYIG devices. The LSSE voltage was found to be enhanced by inserting an ultra-thin Fe$$_{70}$$Cu$$_{30}$$ interlayer. This enhancement decays sharply with increasing the Fe$$_70$$Cu$$_30$$ thickness, suggesting that it is not due to bulk phenomena, such as a superposition of conventional thermoelectric effects, but due to interface effects related to the Fe$$_{70}$$Cu$$_{30}$$ interlayer. Combined with control experiments using Pt/Fe$$_{70}$$Cu$$_{30}$$ devices, we conclude that the enhancement of the LSSE voltage in the Pt/Fe$$_{70}$$Cu$$_{30}$$/BiYIG devices is attributed to the improvement of the spin-mixing conductance at the Pt/BiYIG interfaces.

論文

Longitudinal spin Seebeck effect; From fundamentals to applications

内田 健一*; 石田 真彦*; 吉川 貴史*; 桐原 明宏*; 村上 朝夫*; 齊藤 英治

Journal of Physics; Condensed Matter, 26(34), p.343202_1 - 343202_15, 2014/08

 被引用回数:196 パーセンタイル:84.64(Physics, Condensed Matter)

The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This "longitudinal spin Seebeck effect" (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations.

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