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Wang, Y.*; Gong, W.; Harjo, S.; 他7名*
Acta Materialia, 288, p.120840_1 - 120840_14, 2025/04
被引用回数：8 パーセンタイル：95.60(Materials Science, Multidisciplinary)Low yield strength and the presence of Luders bands constitute principal impediments to the extensive applications of conventional medium Mn steels with a duplex microstructure of ferrite and austenite. Flash heating and the concept of chemical heterogeneity have been combined to engineer a duplex austenite-martensite microstructure in medium Mn steels, which has proven effective in augmenting the yield strength and mitigating the occurrence of Luders bands. However, the underlying mechanisms remain ambiguous. In the present work, the effect of austenite stability on yielding behavior was systematically investigated in an austenite-martensite duplex medium Mn steel. Austenite stability was identified as the critical factor governing yield strength, where reduced stability promotes early stage deformation induced martensite transformation, thereby decreasing yield strength. Diminished austenite stability may as well induce enhanced work hardening, thereby result in the inclination and eventual elimination of yield plateau, concomitant with the disappearance of Luders bands. These observations expand our current understanding of the yielding behavior in medium Mn steels and offer insights for the design of other advanced high strength steels.
堀内 皓斗*; 荒木 康史; 若林 勇希*; 家田 淳一; 山ノ内 路彦*; 他7名*
Advanced Materials, p.2416091_1 - 2416091_9, 2025/00
被引用回数：0 パーセンタイル：0.00(Chemistry, Multidisciplinary)Spin Berry curvature characterizes the band topology as the spin counterpart of Berry curvature and is crucial in generating novel spintronics functionalities. By breaking the crystalline inversion symmetry, the spin Berry curvature is expected to be significantly enhanced; this enhancement will increase the intrinsic spin Hall effect in ferromagnetic materials and, thus, the spin-orbit torques (SOTs). However, this intriguing approach is not applied to devices; generally, the spin Hall effect in ferromagnet/heavy-metal bilayer is used for SOT magnetization switching. Here, SOT-induced partial magnetization switching is demonstrated in a single layer of a single-crystalline Weyl oxide SrRuO
(SRO) with a small current density of 
. Detailed analysis of the crystal structure in the seemingly perfect periodic lattice of the SRO film reveals barely discernible oxygen octahedral rotations with angles of 
near the interface with a substrate. Tight-binding calculations indicate that a large spin Hall conductivity is induced around small gaps generated at band crossings by the synergy of inherent spin-orbit coupling and band inversion due to the rotations, causing magnetization reversal. The results indicate that a minute atomic displacement in single-crystal films can induce strong intrinsic SOTs that are useful for spin-orbitronics devices.
GeTe
nanomeshes小幡 玲二*; 吉川 貴史*; 齊藤 英治; 他7名*
Nanotechnology, 35(47), p.475601_1 - 475601_9, 2024/11
被引用回数：1 パーセンタイル：27.39(Nanoscience & Nanotechnology)The growth of two-dimensional van der Waals magnetic materials presents attractive opportunities for exploring new physical phenomena and valuable applications. Among these materials, FeGeTe
(FGT) exhibits a variety of remarkable properties and has garnered significant attention. Herein, we have for the first time created a nanomesh structure-a honeycomb-like array of hexagonal nanopores-with the zigzag pore-edge atomic structure on thin FGT flakes with and without oxidation of the pore edges. It is revealed that the magnitude of ferromagnetism (FM) significantly increases in both samples compared with bulk flakes without nanomeshes. Critical temperature annealing results in the formation of zigzag pore edges and interpore zigzag-edge nanoribbons. We unveil that the non-oxide (O) termination of the Fe dangling bonds on these zigzag edges enhances FM behavior, while O-termination suppresses this FM by introducing antiferromagnetic behavior through edge O-Fe coupling. FGT nanomeshes hold promise for the creation of strong FM and their effective application in magnetic and spintronic systems.
小澤 孝拓*; 福谷 克之; 他7名*
Nature Communications (Internet), 15, p.9558_1 - 9558_8, 2024/11
被引用回数：2 パーセンタイル：0.00(Multidisciplinary Sciences)Hydrogen, the smallest and lightest element, readily permeates a variety of materials and modulates their physical properties. Identification of the hydrogen lattice location and its amount in crystals is key to understanding and controlling the hydrogen-induced properties. Combining nuclear reaction analysis (NRA) with the ion channeling technique, we experimentally determined the locations of H and D in epitaxial nanofilms of titanium hydrides from the analysis of the two-dimensional angular mappings of NRA yields. Here we show that 11 at% of H are located at the octahedral site with the remaining H atoms in the tetrahedral site. Density functional theory calculations revealed that the structures with the partial octahedral site occupation are stabilized by the Fermi level shift and Jahn-Teller effect induced by hydrogen. In contrast, D was found to solely occupy the tetrahedral site owing to the mass effect on the zero-point vibrational energy. These findings suggest that site occupation of hydrogen can be controlled by changing the isotope mixture ratio, which leads to promising manifestation of novel hydrogen-related phenomena.
Garnaud, L.*; 小川 達彦; 他7名*
EPJ Web of Conferences, 302, p.07004_1 - 07004_14, 2024/10
被引用回数：1 パーセンタイル：0.00(Computer Science, Interdisciplinary Applications)光核反応によって生成される光中性子は、高エネルギーガンマ線源、電子加速器、または原子炉を用いる様々な分野で発生する。光中性子の放出をシミュレートし、その場を特性評価し、あるいは核システムへの影響を評価するため、一般的にモンテカルロ粒子輸送コードが使用される。本研究の目的は、複数のモンテカルロコード(MCNP6、PHITS、およびTRIPOLI-4)を用いて光中性子のシミュレーションに関するデータ集を作成することである。各コードは、ENDF/B-VIII.0およびJENDL-5核データライブラリを用いて順次実行される。反応エネルギー閾値から30MeVまで、すなわち巨大双極子共鳴(GDR)の領域において、自然同位体組成を持つ50の元素によって生成される光中性子場を扱った。光中性子場は、光中性子電流、エネルギースペクトル、および角度分布という3つの観測量に従って特性評価した。本稿では、原子番号の昇順で最初の5つの元素、すなわち重水素、ベリリウム、炭素、窒素、および酸素について得られた結果を提示した。
substrate小幡 玲二*; 齊藤 英治; 吉川 貴史; 他7名*
Advanced Materials, 36(19), p.2311339_1 - 2311339_8, 2024/05
被引用回数：1 パーセンタイル：27.39(Chemistry, Multidisciplinary)SrTiO (STO) substrate, a perovskite oxide material known for its high dielectric constant (epsilon), facilitates the observation of various (high-temperature) quantum phenomena. A quantum Hall topological insulating (QHTI) state, comprising two copies of QH states with antiparallel two ferromagnetic edge-spin overlap protected by the U(1) axial rotation symmetry of spin polarization, has recently been achieved in low magnetic field (B) even as high as approximate to 100 K in a monolayer graphene/thin hexagonal boron nitride (hBN) spacer placed on an STO substrate, thanks to the high epsilon of STO. Despite the use of the heavy STO substrate, however, proximity-induced quantum spin Hall (QSH) states in 2D TI phases, featuring a topologically protected helical edge spin phase within time-reversal-symmetry, is not confirmed. Here, with the use of a monolayer hBN spacer, it is revealed the coexistence of QSH (at B = 0T) and QHTI (at B not equal 0) states in the same single graphene sample placed on an STO, with a crossover regime between the two at low B. It is also classified that the different symmetries of the two nontrivial helical edge spin phases in the two states lead to different interaction with electron-puddle quantum dots, caused by a local surface pocket of the STO, in the crossover regime, resulting in a spin dephasing only for the QHTI state. The results obtained using STO substrates open the doors to investigations of novel QH spin states with different symmetries and their correlations with quantum phenomena. This exploration holds value for potential applications in spintronic devices.
and 
shell gap for Ti and V by the first high-precision multireflection time-of-flight mass measurements at BigRIPS-SLOWRI飯村 俊*; Rosenbusch, M.*; 高峰 愛子*; 角田 佑介*; 和田 道治*; Chen, S.*; Hou, D. S.*; Xian, W.*; 石山 博恒*; Yan, S.*; et al.
Physical Review Letters, 130(1), p.012501_1 - 012501_6, 2023/01
被引用回数：15 パーセンタイル：87.12(Physics, Multidisciplinary)The atomic masses of 
Sc, 
Ti, and 
V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For Ti and V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species 
Ti and 
V. With the new precision achieved, we reveal the nonexistence of the empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied 
p
orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the d
and g
orbits and compare the results with conventional shell model calculations, which exclude the g and the d orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at 
.
Ti
O
梅垣 いづみ*; 杉山 純; 他7名*
Journal of Physical Chemistry C, 126(25), p.10506 - 10514, 2022/06
被引用回数：5 パーセンタイル：24.86(Chemistry, Physical)To study an intrinsic self-diffusion coefficient of Li ion in a battery anode material, spinel LiTiO, negative and positive muon spin rotation and relaxation (
SR) spectra were measured. The implanted 
in this study locates at an interstitial site near the O
ion to form an O-H like bond, whereas the implanted 
is mainly captured by an oxygen nucleus, resulting in muonic oxygen formation. The at an interstitial site is known to diffuse at high temperatures. Nevertheless, the muonic oxygen is immobile until the spinel decomposition temperature. The field fluctuation rate determined with SR increased with increasing temperature above 200 K with a 0.08(5) eV thermal activation energy. The field fluctuation rate curves obtained by and agreed well.
大谷 将士*; 近藤 恭弘; 齊藤 直人; 長谷川 和男; 他7名*; J-PARC E34 Collaboration*
JPS Conference Proceedings (Internet), 25, p.011027_1 - 011027_5, 2019/03
ミュオン加速のための加速器を開発中である。この加速器により、ミュオンの異常磁気モーメントを0.1ppmの精度で、また電気双極子モーメントを10
cmの精度で測定することが可能となり、素粒子の標準理論をこえる物理の探索ができるようになる。最初のステップとして、ミュオンの加速試験を行う予定である。そのための負ミュオニウム源を開発し、既存のJ-PARC RFQ予備機を用いる。また、それに続く低ベータおよび中ベータ加速空洞も開発中である。低ベータにはinterdigital H構造、中ベータにはdisk and washer structureを用いる。本論文では、ミュオン加速試験の準備状況および、加速空洞の開発状況について述べる。
hyperon capture at rest in nuclear emulsionTheint, 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
被引用回数：6 パーセンタイル：42.15(Physics, Multidisciplinary)In the E373 experiment at KEK-PS, we have located nearly 
stopping events of 
hyperon candidates in nuclear emulsion. Among them, the identification of 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 stopping events to be 
with 3.2% systematic error. The trapping probabilities of two 
hyperons for light and heavy nuclei were found to be 
% and 
%, respectively. For at least one trapping, the probabilities were 
% and 
% for light and heavy nuclei. These results are the first time to present the trapping probabilities of hyperons via hyperon capture at rest in the emulsion.
熊田 高之; 他7名*
JPS Conference Proceedings (Internet), 22, p.011015_1 - 011015_5, 2018/11
Conventional deuterium contrast variation neutron reflectometry (NR) sometimes misleads when the deuterated SIMULATION samples fail to reproduce the structure of the REAL ones by delicate techniques such as spin-coating. On the other hand, the Spin contrast variation (SCV)-NR determines the structure from PH-dependent NR profiles of REAL samples. Therefore, the SCV-NR works not only as a technique which omits the cost of deuterium substitution, but also as a reliable technique to determine multi-layered surface and interface structure.
Wang, B.*; He, H.*; Naeem, M.*; Lan, S.*; Harjo, S.; 川崎 卓郎; Nie, Y.*; Wang, X.-L.*; 他7名*
Scripta Materialia, 155, p.54 - 57, 2018/10
被引用回数：72 パーセンタイル：94.70(Nanoscience & Nanotechnology)The deformation behavior of an equi-atomic face-centered-cubic CoCrFeNi high entropy alloy was investigated by in-situ neutron diffraction under tensile loading up to 40% applied strain. A three-stage deformation behavior was fully captured by lattice strain and texture evolution. In spite of the chemical complexity, the deformation in CoCrFeNi is dominated by dislocation activities. Analysis of diffraction and microscopy data shows that the deformation progresses from dislocation slip to severe entanglement, where a sharp increase in dislocation density was observed. The neutron diffraction data, corroborated by transmission electron microscopy analysis, provided microscopic insights of the previously reported three-stage hardening behavior.
白方 敬章*; 山本 敏久*; 中島 文明*; 他7名*
PNC TN2410 89-003, 349 Pages, 1989/03
本報告書は,動力炉研究開発本部 炉技術開発Grで組織しているJUPITERサブワーキングGrの昭和63年度の成果をまとめたものである。JUPITERサブワーキングGrは,動燃事業団が米国エネルギー省(DOE)との共同研究としてアルゴンヌ国立研究所(ANL-W)の大型臨界実験装置ZPPRで実施した大型高速炉物理実験JUPITER-III計画の計画,実験解析を行うためのワーキンググループである。JUPITER-III計画は電気出力65万キロワット相当の軸方向非均質炉心模擬実験(ZPPR-17シリーズ)と100万キロワット相当の均質炉心模擬実験(ZPPR-18シリーズ)からなる。ZPPR-17シリーズの実験解析は本年度でほぼ完了し,ZPPR-18シリーズについては実験解析の準備中である。本年度の主な成果は下記の通りである。(1) 昨年度に引き続き,ZPPR-17の実験解析を実施し,以下の成果を得た。(I)臨界性について,マルチドロワモデル及びセンターラインモデル(セル定数作成法)の効果を評価した。前者の効果は+0.17%
kであり,後者の効果は基準解析のプレートストレッチモデルに比べて0.08
0.09%k高目である。これらの結果を考慮した解析結果(C/E値)は均質炉心ZPPR-9及び径方向非均質炉心ZPPR-13Aの結果とほぼ一致した。(II)制御棒反応度価値のC/E値は中心で0.9程度であり,5%程度の径方向依存性がみられた。反応率分布のC/E値にも510%の径方向依存性があり,これらの傾向は均質炉心と同様である。(III)広領域NaボイドのC/E値は炉心領域で1.21.5であり,内部ブランケット領域は0.8程度と低目である。サンプル反応度についても内部ブランケット領域では炉心領域よりも239Puサンプルで20%,10Bサンプルで10%程度過小評価する。これらの傾向は径方向非均質炉心と同様である。(2) ZPPR-17の実験データ集について,その構成と記載内容について検討し,記載すべきデータ項目を選定した。さらに,代表的な実験項目について具体的な記載内容をまとめた。(3) JUPITER実験等の臨界実験データとの対比及び補完の観点から,将来の「常陽」による炉物理実験項目を洗い出し,その成立性及び実験のために具備すべき実験機能を検討した
