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Enhancement of electrical conductivity to metallization of Mn$$_{3-x}$$Fe$$_x$$O$$_4$$ spinel and postspinel with elevating pressure

山中 高光*; Rahman, S.*; 中本 有紀*; 服部 高典; Jang, B. G.*; Kim, D. Y.*; Mao, H.-K.*

Journal of Physics and Chemistry of Solids, 167, p.110721_1 - 110721_10, 2022/08



Regulation of strength and ductility of single-phase twinning-induced plasticity high-entropy alloys

Wei, D.*; Gong, W.; 川崎 卓郎; Harjo, S.; 加藤 秀実*

Scripta Materialia, 216, p.114738_1 - 114738_6, 2022/07

Near-equiatomic single-phase twining-induced plasticity (TWIP) high-entropy alloys (HEAs) exhibit a good combination of strength and ductility, but their modest yield strength requires further improvement. Here, we propose a strategy for markedly enhancing their strength while retaining satisfactory ductility, taking advantage of the temperature dependence of the stacking fault energy. The room-temperature strength of a representative TWIP HEA was improved by the cryogenic pre-deformation-induced dislocations, martensite, nanotwins, and stacking faults. The tensile properties were further tuned by subsequent annealing to obtain partially recovered or recrystallized microstructures. The influence of regulated microstructures on the yield strength was clarified by neutron diffraction line profile analysis. This study presents possibilities for fabricating advanced HEAs by tuning the substructures.


Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

Tang, J.*; Seo, O.*; Rivera Rocabado, D. S.*; 小板谷 貴典*; 山本 達*; 難波 優輔*; Song, C.*; Kim, J.*; 吉越 章隆; 古山 通久*; et al.

Applied Surface Science, 587, p.152797_1 - 152797_8, 2022/06



Analysis of the electric double layer structure formed in an ionic liquid using neutron reflectivity

田村 和久; 阿久津 和宏*; Cagnes, M.*; Darwish, T. A.*

ECS Advances (Internet), 1(2), p.020503_1 - 020503_5, 2022/06

中性子反射率測定によりイオン液体/Si電極界面の構造を調べた。部分的に重水素化した1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([BMIM]TFSA)を用いて、[BMIM]TFSA/Si(100)界面における、イオン液体分子の配向を調べた。実験結果は、負に帯電しているSi(100)電極表面では、電極表面に吸着しているイオン液体分子は、表面に平行に配向していることが分かった。



遠藤 章

Isotope News, (781), P. 3, 2022/06

日本原子力研究開発機構原子力科学研究所の研究用原子炉JRR-3は、2021年2月に10年ぶりに運転を再開した。その後調整運転を経て、7月から11月まで実験装置や照射設備の利用を行い、2021年の運転を計画通り終了した。この期間、Ir-192, Au-198を製造し治療用に供給するとともに、Mo-99製造に向けた試験照射にも着手した。これは、東日本大震災以降、国内で止まっていた原子炉によるRI製造の再開である。本稿では、JRR-3を利用した医療用RI製造の今後の取り組みについて紹介する。


Small-angle neutron scattering by spatially inhomogeneous ferromagnets with a nonzero average uniaxial anisotropy

Zaporozhets, V. D.*; 大場 洋次郎; Michels, A.*; Metlov, K. L.*

Journal of Applied Crystallography, 55(3), p.592 - 600, 2022/06

Micromagnetic theory well explains the magnetic small-angle neutron scattering (SANS) data of bulk ferromagnets. However, only the samples having random magnetic anisotropy are mainly handled. In this study, the micromagnetic SANS theory is extended to allow to analyze uniaxial magnetic anisotropy. Micromagnetic response functions for SANS are computed analytically for several practical arrangements of anisotropy and external magnetic field orientations. This theory agrees well with the experimental SANS data of a practical soft magnet and plastically-deformed Ni and successfully provides the uniaxial anisotropy quality factors.


Various ordered states in Heisenberg FCC antiferromagnets with dipole-dipole interactions

横田 光史

Journal of the Physical Society of Japan, 91(6), p.064003_1 - 064003_7, 2022/06

Heisenberg antiferromagnet on a face-centered cubic (fcc) lattice with a nearest-neighbor exchange interaction is known to order antiferromagnetically with type-I spin structure. On the other hand, Heisenberg magnet on a fcc lattice with only magnetic dipole-dipole interactions orders ferromagnetically. Both the antiferromagnetic nearest-neighbor exchange interaction and the dipole-dipole interactions introduce frustration into the Heisenberg magnets but differently. Here the Heisenberg fcc antiferromagnets, in which both interactions are included are investigated by numerically solving the Landau-Lifshitz (LL) equation. Various ordered states which include multi-K structures are obtained depending on the relative strength of the two kinds of interactions.


Quantitative X-ray diffraction analysis of solute-enriched stacking faults in $$hcp$$-Mg alloys based on peak asymmetry analysis

江草 大佑*; 眞鍋 怜*; 川崎 卓郎; Harjo, S.; 佐藤 成男*; 阿部 英司*

Materials Today Communications (Internet), 31, p.103344_1 - 103344_6, 2022/06

Based on X-ray diffraction analysis we attempt to quantify a volume fraction of stacking faults, which are essentially enriched by solute elements (solute-enriched stacking faults; SESFs) in Mg-Zn-Gd alloys with a hexagonal-close-packed ($$hcp$$) structure. We find that the SESFs with a local face-center-cubic stacking mostly occurs as a limited thickness less than several unit-cell dimensions, causing anisotropic broadening of the diffraction peaks including $$c*$$-component. By dealing the SESFs as intergrowth-like precipitates, we have successfully decomposed the asymmetric peak profile into the $$hcp$$-matrix and the SESF peaks, by which the relevant volume fractions can be estimated in a highly quantitative manner.


Beam emittance growth due to the strong space-charge field at low energy of a high-intensity ion linac and its mitigation using an octupole magnetic field

地村 幹; 原田 寛之; 金正 倫計

Progress of Theoretical and Experimental Physics (Internet), 2022(6), p.063G01_1 - 063G01_26, 2022/06



Improvement of neutron diffraction at compact accelerator-driven neutron source RANS using peak profile deconvolution and delayed neutron reduction for stress measurements

岩本 ちひろ*; 高村 正人*; 上野 孝太*; 片岡 美波*; 栗原 諒*; 徐 平光; 大竹 淑恵*

ISIJ International, 62(5), p.1013 - 1022, 2022/05

Neutron diffraction is a powerful non-destructive method for evaluating the microscopic structure and internal stress of metal plates as a bulk average. Precise neutron diffraction measurements with a high intensity neutron beam have already been carried out at large-scale neutron facilities. However, it is not easy to provide users with enough experimental opportunities. We are working on upgrading the neutron diffractometer with techniques of time-of-flight to enable stress measurements at RIKEN accelerator-driven compact neutron source (RANS). To improve neutron diffraction resolution, delayed neutrons, which expand neutron beam pulse width, should be suppressed. However, it is difficult to separate the delayed neutrons experimentally. In this study, a new analysis method has been proposed to deconvolute the diffraction peak from the delayed neutron component. Moreover, a new collimator system, called decoupled collimator system, has been developed to reduce the number of delayed neutrons. The diffraction patterns from a powder sample of pure body-centered cubic iron were measured with the decoupled collimator and the diffraction peak of {211} reflection was analyzed by the new analysis method using a model function of a single exponential decay function convoluted with a Gaussian function. By this method, the decoupled collimator system has been confirmed to achieve a smaller measurement limit of lattice strain $$Delta$$$$varepsilon$$ than a small-aperture polyethylene collimator system and a non-collimator system. The currently available $$Delta$$$$varepsilon$$ was 6.7$$times$$10$$^{-4}$$, this means that the internal stress up to 130 MPa can be well evaluated for steel materials with a Young's modulus of 200 GPa at RANS.


Hyperfine splitting and nuclear spin polarization in NdPd$$_5$$Al$$_2$$ and Nd$$_3$$Pd$$_{20}$$Ge$$_6$$

目時 直人; 柴田 薫; 松浦 直人*; 北澤 英明*; 鈴木 博之*; 山内 宏樹; 萩原 雅人; Frontzek, M. D.*; 松田 雅昌*

Journal of the Physical Society of Japan, 91(5), p.054710_1 - 054710_6, 2022/05

NdPd$$_5$$Al$$_2$$におけるNdの超微細相互作用分裂を高分解能の中性子非弾性散乱によって研究した。Nd核の核スピン($$I$$=7/2)と、$$|pm9/2rangle$$の軌道が主成分の$$Gamma_6$$基底状態を示す4$$f$$電子との間の超微細相互作用によって、磁気秩序相において生じた超微細相互作用分裂に起因する中性子非弾性散乱ピークを、$$hbaromega$$ = $$pm$$3$$mu$$eVのエネルギーに観察した。低温では、Nd核スピンの低エネルギー状態の占拠確率が増加することによりNd核スピンが偏極し、反強磁性散乱ピーク強度に寄与するが、その際、中性子の非スピン反転過程の寄与が最も大きい。この現象の応用として反強磁性散乱ピーク強度の温度変化から、Nd$$_3$$Pd$$_{20}$$Ge$$_6$$のNd磁気モーメント及び超微細相互作用分裂の大きさを見積もることに成功した。



大原 高志

日本結晶学会誌, 64(2), p.132 - 139, 2022/05



Impedance reduction by a SiC-loaded flange and its application to the J-PARC main ring septum magnet

小林 愛音*; 外山 毅*; 中村 剛*; 菖蒲田 義博; 石井 恒次*

Nuclear Instruments and Methods in Physics Research A, 1031, p.166515_1 - 166515_12, 2022/05

現在、大強度陽子加速器施設(J-PARC)のメインリングでは、ビームパワーの増強が進められている。大強度ビーム実現のためには、ビームパワーを制限するビーム不安定性の低減と、その発生源であるビーム結合インピーダンスの低減が不可欠である。3次元シミュレーションコード(CST studio suite)によれば、現在のセプタム電磁石は大きなインピーダンスになる。今回、このセプタム電磁石は、より高い繰り返し回数に対応するため新型の電磁石に置き換える予定なので、これにあわせてインピーダンスの低減法を考案した。一般的に、テーパー管を使うことでインピーダンスは低減されることが知られているが、実際に設置するには空間的に非常に強い制限をうける。そこで、セプタム電磁石のフランジに銅板とSiCを取り付けることで、簡単にしかも効果的にインピーダンスを低減できる手法を考案した。これにより、新型セプタム電磁石の縦方向インピーダンスは対策をしない場合と比べて1%に減少し、ビーム安定条件が大きく改善した。この方法は、フランジに省スペースで設置できるため、本来の電磁石の発生磁場に影響を与えることなく、インピーダンスを低減できる。また、ビームパイプの形状に関係なく幅広く適応できる。


Damped Dirac magnon in the metallic kagome antiferromagnet FeSn

Do, S.-H.*; 金子 耕士; 梶本 亮一; 蒲沢 和也*; Stone, M. B.*; Lin, J. Y. Y.*; 伊藤 晋一*; 益田 隆嗣*; Samolyuk, G. D.*; Dagotto, E.*; et al.

Physical Review B, 105(18), p.L180403_1 - L180403_6, 2022/05

We report inelastic neutron scattering studies of the prototypical kagome magnetic metal FeSn. The spectra display well defined spin waves extending up to 120 meV. Above this energy, the spin waves become progressively broadened, reflecting interactions with the Stoner continuum. Using linear spin wave theory, we determine an effective spin Hamiltonian that explains the measured dispersion. This analysis indicates that the Dirac magnon at the K point occurs on the brink of a region where well defined spin waves become unobservable. Our results emphasize the influential role of itinerant carriers on the topological spin excitations of metallic kagome magnets.


Two-dimensional resistive-wall impedance with finite thickness; Its mathematical structures and their physical meanings

菖蒲田 義博

Progress of Theoretical and Experimental Physics (Internet), 2022(5), p.053G01_1 - 053G01_44, 2022/05



Marking actinides for separation: Resonance-enhanced multiphoton charge transfer in actinide complexes

松田 晶平; 横山 啓一; 矢板 毅; 小林 徹; 金田 結依; Simonnet, M.; 関口 哲弘; 本田 充紀; 下条 晃司郎; 土井 玲祐; et al.

Science Advances (Internet), 8(20), p.eabn1991_1 - eabn1991_11, 2022/05



Evaluation of titanium vacuum chamber as getter pump

神谷 潤一郎; 高野 一弘*; 油座 大夢*; 和田 薫

e-Journal of Surface Science and Nanotechnology (Internet), 20(2), p.107 - 118, 2022/05



Fabrication of (Bi$$_2$$)$$_m$$(Bi$$_2$$Te$$_3$$)$$_n$$ superlattice films by Te desorption from a pristine Bi$$_2$$Te$$_3$$ film

日下 翔太郎*; 佐々木 泰祐*; 角田 一樹; 一ノ倉 聖*; 出田 真一郎*; 田中 清尚*; 宝野 和博*; 平原 徹*

Applied Physics Letters, 120(17), p.173102_1 - 173102_5, 2022/04

We fabricated superlattice films composed of Bi$$_2$$ bilayers (BLs) and Bi$$_2$$Te$$_3$$ quintuple layers (QLs) by annealing pure Bi$$_2$$Te$$_3$$ films. It was found that Te desorbs from the QL to form the BL with an activation energy of 2.7 eV. Eventually two distinct stoichiometric phases were formed, Bi$$_1$$Te$$_1$$ (QL-BL-QL) and Bi$$_4$$Te$$_3$$ (QL-BL), as evidenced by scanning transmission emission microscopy measurements. The surface-state dispersion was measured with angle-resolved photoemission spectroscopy and the topological nature of each sample is discussed. Our method offers a convenient and simple way to fabricate superlattice films with different topological properties.


Cross-scale analysis of temperature compensation in the cyanobacterial circadian clock system

古池 美彦*; Ouyang, D.*; 富永 大輝*; 松尾 龍人*; 向山 厚*; 川北 至信; 藤原 悟*; 秋山 修志*

Communications Physics (Internet), 5(1), p.75_1 - 75_12, 2022/04

Circadian clock proteins often reveal temperature-compensatory responses that counteract temperature influences to keep their enzymatic activities constant over a physiological range of temperature. This temperature-compensating ability at the reaction level is likely crucial for circadian clock systems, to which the clock proteins are incorporated, to achieve the system-level temperature compensation of the oscillation frequency. Nevertheless, temperature compensation is yet a puzzling phenomenon, since side chains that make up the clock proteins fluctuate more frequently due to greater thermal energy at higher temperature. Here, we investigated temperature influences on the dynamics of KaiC, a temperature-compensated enzyme (ATPase) that hydrolyzes ATP into ADP in the cyanobacterial circadian clock system, using quasielastic neutron scattering. The frequency of picosecond to subnanosecond incoherent local motions in KaiC was accelerated by a factor of only 1.2 by increasing the temperature by 10$$^{circ}$$C. This temperature insensitivity of the local motions was not necessarily unique to KaiC, but confirmed also for a series of temperature-sensitive mutants of KaiC and proteins other than clock-related proteins. Rather, the dynamics associated with the temperature-compensatory nature of the reaction- and system-level was found in global diffusional motions, which was suggested to regulate the temperature dependence of ATPase activity and dephosphorylation process presumably through changes in the hexamer conformation of KaiC. The spatiotemporal scale at which cross-scale causality of the temperature sensitivity is established is finite, and extends down to picosecond to subnanosecond dynamics only in a very limited part of KaiC, not in its entire part.


${it Operando}$ structure observation of pyroelectric ceramics during power generation cycle

川崎 卓郎; 福田 竜生; 山中 暁*; 坂本 友和*; 村山 一郎*; 加藤 孝典*; 馬場 将亮*; 橋本 英樹*; Harjo, S.; 相澤 一也; et al.

Journal of Applied Physics, 131(13), p.134103_1 - 134103_7, 2022/04

The microscopic origin of the pyroelectric power generation using ferroelectric ceramics for energy harvesting from time-varying waste heat can be understood by conducting ${it operando}$ neutron diffraction measurements. The behavior of the domain orientation and lattice strain in the lead zirconate titanate (PZT)-based ceramics with a tetragonal structure during the novel power generation cycle combining electric field and temperature change were investigated. The [001] domains and the lattice strain of the (111) plane in the direction of parallel to the electric field increase in the process of simultaneous rise in the electric field and temperature, and rapidly decrease in the process of the field drop. The alignment of the domain orientation by the electric field and its randomization by the higher temperature during the cycle are critical features of the current power generation system.

19773 件中 1件目~20件目を表示