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A First glimpse at the shell structure beyond $$^{54}$$Ca; Spectroscopy of $$^{55}$$K, $$^{55}$$Ca, and $$^{57}$$Ca

小岩井 拓真*; Wimmer, K.*; Doornenbal, P.*; Obertelli, A.*; Barbieri, C.*; Duguet, T.*; Holt, J. D.*; 宮城 宇志*; Navr$'a$til, P.*; 緒方 一介*; et al.

Physics Letters B, 827, p.136953_1 - 136953_7, 2022/04

中性子過剰核$$^{54}$$Caでは、新魔法数34が発見されて以来、その構造を知るために多くの実験がなされてきたが、それを超える中性子過剰核の情報は全く知られてこなかった。本論文では、理化学研究所RIBFにて$$^{55}$$K, $$^{55}$$Ca, $$^{57}$$Caの励起状態から脱励起するガンマ線を初めて観測した結果を報告した。それぞれ1つのガンマ線しか得られなかったものの、$$^{55}$$Kおよび$$^{55}$$Caのデータは、それぞれ、陽子の$$d_{3/2}$$$$s_{1/2}$$軌道間のエネルギー差、中性子の$$p_{1/2}$$$$f_{5/2}$$軌道間のエネルギー差を敏感に反映し、両方とも最新の殻模型計算によって200keV程度の精度で再現できることがわかった。また、1粒子状態の程度を特徴づける分光学的因子を実験データと歪曲波インパルス近似による反応計算から求め、その値も殻模型計算の値と矛盾しないことがわかった。


Activities of the GIF safety and operation project of the sodium-cooled fast reactors

山野 秀将; Tsige-Tamirat, H.*; Kang, S. H.*; Summer, T.*; Chenaud, M. S.*; Rozhikhin, E.*; Wang, J.*

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Sustainable Clean Energy for the Future (FR22) (Internet), 9 Pages, 2022/04



Temperature-dependent hardening contributions in CrFeCoNi high-entropy alloy

Naeem, M.*; He, H.*; Harjo, S.; 川崎 卓郎; Lin, W.*; Kai, J.-J.*; Wu, Z.*; Lan, S.*; Wang, X.-L.*

Acta Materialia, 221, p.117371_1 - 117371_18, 2021/12

We studied the deformation behavior of CrFeCoNi high-entropy alloy by in situ neutron diffraction at room temperature, intermediate low temperature of 140 K, low temperatures of 40 K (no serrated deformation) and 25 K (with massive serrations). The contributions from different deformation mechanisms to the yield strength and strain hardening have been estimated. The athermal contributions to the yield strength were $$sim$$183 MPa at all temperatures, while the Peierls stress increased significantly at low temperatures (from 148 MPa at room temperature to 493 MPa at 25 K). Dislocations contributed to $$sim$$94% strain hardening at room temperature. Although the dislocation strengthening remained the major hardening mechanism at very low temperatures, the planar faults contribution increased steadily from 6% at room temperature to 28% at 25 K.


Crystalline fully carboxylated polyacetylene obtained under high pressure as a Li-ion battery anode material

Wang, X.*; Tang, X.*; Zhang, P.*; Wang, Y.*; Gao, D.*; Liu, J.*; Hui, K.*; Wang, Y.*; Dong, X.*; 服部 高典; et al.

Journal of Physical Chemistry Letters (Internet), 12(50), p.12055 - 12061, 2021/12



Long decay length of magnon-polarons in BiFeO$$_{3}$$/La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ heterostructures

Zhang, J.*; Chen, M.*; Chen, J.*; 山本 慧; Wang, H.*; Hamdi, M.*; Sun, Y.*; Wagner, K.*; He, W.*; Zhang, Y.*; et al.

Nature Communications (Internet), 12(1), p.7258_1 - 7258_8, 2021/12

Magnons can transfer information in metals and insulators without Joule heating, and therefore are promising for low-power computation. The on-chip magnonics however suffers from high losses due to limited magnon decay length. In metallic thin films, it is typically on the tens of micrometre length scale. Here, we demonstrate an ultra-long magnon decay length of up to one millimetre in multiferroic/ferromagnetic BiFeO$$_{3}$$(BFO)/La$$_{0.67}$$Sr$$_{0.33}$$MnO$$_{3}$$ (LSMO) heterostructures at room temperature. This decay length is attributed to a magnon-phonon hybridization and is more than two orders of magnitude longer than that of bare metallic LSMO. The long-distance modes have high group velocities of 2.5 km$$^{-1}$$ as detected by time-resolved Brillouin light scattering. Numerical simulations suggest that magnetoelastic coupling via the BFO/LSMO interface hybridizes phonons in BFO with magnons in LSMO. Our results provide a solution to the long-standing issue on magnon decay lengths in metallic magnets and advance the bourgeoning field of hybrid magnonics.


The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10


The long-lived $$^{60}$$Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe on $$^{59}$$Fe (half-life=44.5 days) is the key reaction for the production of $$^{60}$$Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 $$gamma$$-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5$$pm$$3.5 mb at $$kT$$ = 30 keV and 13.4$$pm$$1.7 mb at $$kT$$ = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of $$^{60}$$Fe from the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe rate are at most 25$$%$$. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of $$^{60}$$Fe.


Investigation of the ground-state spin inversion in the neutron-rich $$^{47,49}$$Cl isotopes

Linh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Chen, S.*; Chung, L. X.*; Duguet, T.*; G$'o$mez-Ramos, M.*; et al.

Physical Review C, 104(4), p.044331_1 - 044331_16, 2021/10



Martensitic transformation in CrCoNi medium-entropy alloy at cryogenic temperature

Naeem, M.*; Zhou, H.*; He, H.*; Harjo, S.; 川崎 卓郎; Lan, S.*; Wu, Z.*; Zhu, Y.*; Wang, X.-L.*

Applied Physics Letters, 119(13), p.131901_1 - 131901_7, 2021/09

We investigated the in situ deformation behavior of the CrCoNi medium-entropy alloy at a cryogenic temperature of 140 K and compared it with deformation at room temperature. The sample exhibited higher strength and larger ductility at the cryogenic temperature. The CrCoNi alloy remained single-phase face-centered cubic at room temperature, while deformation at 140 K resulted in a martensitic transformation to the hexagonal close-packed structure. The phase transformation, an additional deformation mechanism to stacking faults, twinning, and dis- location slip, resulted in a higher work hardening at cryogenic temperature. The study addresses the structure metastability in the CrCoNi alloy, which led to the formation of epsilon-martensite from the intrinsic stacking faults.


Spin-flop phase in a honeycomb antiferromagnet Mn$$_{0.84}$$Mg$$_{0.16}$$TiO$$_{3}$$

社本 真一; 山内 宏樹; 池内 和彦*; Lee, M. K.*; Chang, L.-J.*; Garlea, V. O.*; Hwang, I. Y.*; Lee, K. H.*; Chung, J.-H.*

Journal of the Physical Society of Japan, 90(9), p.093703_1 - 093703_4, 2021/09

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



Activities of the GIF safety and operation project of sodium-cooled fast reactor systems

山野 秀将; Chenaud, M.-S.*; Kang, S.-H.*; Sumner, T.*; Tsige-Tamirat, H.*; Wang, J.*; Rozhikhin, E.*

Proceedings of 28th International Conference on Nuclear Engineering; Nuclear Energy the Future Zero Carbon Power (ICONE 28) (Internet), 8 Pages, 2021/08



Pairing forces govern population of doubly magic $$^{54}$$Ca from direct reactions

Browne, F.*; Chen, S.*; Doornenbal, P.*; Obertelli, A.*; 緒方 一介*; 宇都野 穣; 吉田 数貴; Achouri, N. L.*; 馬場 秀忠*; Calvet, D.*; et al.

Physical Review Letters, 126(25), p.252501_1 - 252501_7, 2021/06

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



Optimization of a slab geometry type cold neutron moderator for RIKEN accelerator-driven compact neutron source

Ma, B.*; 勅使河原 誠; 若林 泰生*; Yan, M.*; 橋口 隆生*; 山形 豊*; Wang, S.*; 池田 裕二郎*; 大竹 淑恵*

Nuclear Instruments and Methods in Physics Research A, 995, p.165079_1 - 165079_7, 2021/04

理研加速器駆動型小型中性子源における冷中性子モデレータの最適化を行った。安全かつ管理の容易な物質であるメシチレンをモレデータ材として選択し、粒子・重イオン輸送計算コードシステム(PHITS)を用いて、20Kメシチレンモデレータに室温ポリエチレン(PE)プレモデレータ組み合わせ、スラブ形状で結合した冷中性子の最適化を行った。冷中性子強度を増加させるために、メシチレンとPEの厚さ, 反射体、及び遮へい配置のパラメータを検討した。中性子発生ターゲットから2mの位置で冷中性子強度1.15$$times$$10$$^{3}$$n/cm$$^{2}$$/$$mu$$Aを達成した。これは現在のPEモデレータの12倍である。メシチレンが冷中性子モデレータ材料として魅力的なモデレータ材であることを示した。


First spectroscopic study of $$^{51}$$Ar by the ($$p$$,2$$p$$) reaction

Juh$'a$sz, M. M.*; Elekes, Z.*; Sohler, D.*; 宇都野 穣; 吉田 数貴; 大塚 孝治*; 緒方 一介*; Doornenbal, P.*; Obertelli, A.*; 馬場 秀忠*; et al.

Physics Letters B, 814, p.136108_1 - 136108_8, 2021/03

 被引用回数:1 パーセンタイル:74.98(Astronomy & Astrophysics)

($$p$$,$$2p$$)反応と$$gamma$$線分光を用いて$$^{51}$$Arの束縛状態と非束縛状態の核構造研究を行った。実験結果と殻模型計算を比較することで、2つの束縛状態と6つの非束縛状態を決定した。$$^{51}$$Arの束縛状態を生成する反応断面積が小さいことから、これは中性子数32, 34の顕著なsub-shell closureが存在している確かな証拠と解釈できる。


Spin-orbit-induced Ising ferromagnetism at a van der Waals interface

松岡 秀樹*; Barnes, S. E.*; 家田 淳一; 前川 禎通; Bahramy, M. S.*; Saika, B. K.*; 竹田 幸治; 和達 大樹*; Wang, Y.*; 吉田 訓*; et al.

Nano Letters, 21(4), p.1807 - 1814, 2021/02

 被引用回数:1 パーセンタイル:72.02(Chemistry, Multidisciplinary)

Magnetocrystalline anisotropy, a key ingredient for establishing long-range order in a magnetic material down to the two-dimensional (2D) limit, is generally associated with spin-orbit interaction (SOI) involving a finite orbital angular momentum. Here we report strong out-of-plane magnetic anisotropy without orbital angular momentum, emerging at the interface between two different van der Waals (vdW) materials, an archetypal metallic vdW material NbSe$$_{2}$$ possessing Zeeman-type SOI and an isotropic vdW ferromagnet V$${}_5$$Se$${}_8$$. We found that the Zeeman SOI in NbSe$$_{2}$$ induces robust out-of-plane magnetic anisotropy in V$$_{5}$$Se$$_{8}$$ down to the 2D limit with a more than 2-fold enhancement of the transition temperature. We propose a simple model that takes into account the energy gain in NbSe$$_{2}$$ in contact with a ferromagnet, which naturally explains our observations. Our results demonstrate a conceptually new magnetic proximity effect at the vdW interface, expanding the horizons of emergent phenomena achievable in vdW heterostructures.


Stacking fault driven phase transformation in CrCoNi medium entropy alloy

He, H.*; Naeem, M.*; Zhang, F.*; Zhao, Y.*; Harjo, S.; 川崎 卓郎; Wang, B.*; Wu, X.*; Lan, S.*; Wu, Z.*; et al.

Nano Letters, 21(3), p.1419 - 1426, 2021/02

 被引用回数:3 パーセンタイル:0(Chemistry, Multidisciplinary)

In CrCoNi, a so-called medium-entropy alloy, an fcc-to-hcp phase transformation has long been anticipated. Here, we report an in situ loading study with neutron diffraction, which revealed a bulk fcc-to-hcp phase transformation in CrCoNi at 15 K under tensile loading. By correlating deformation characteristics of the fcc phase with the development of the hcp phase, it is shown that the nucleation of the hcp phase was triggered by intrinsic stacking faults. The confirmation of a bulk phase transformation adds to the myriads of deformation mechanisms available in CrCoNi, which together underpin the unusually large ductility at low temperatures.


$$N$$ = 32 shell closure below calcium; Low-lying structure of $$^{50}$$Ar

Cort$'e$s, M. L.*; Rodriguez, W.*; Doornenbal, P.*; Obertelli, A.*; Holt, J. D.*; Men$'e$ndez, J.*; 緒方 一介*; Schwenk, A.*; 清水 則孝*; Simonis, J.*; et al.

Physical Review C, 102(6), p.064320_1 - 064320_9, 2020/12

 被引用回数:1 パーセンタイル:35.83(Physics, Nuclear)

理化学研究所RIBFにおいて、$$N$$=32同位体である$$^{50}$$Arの低励起構造を陽子・中性子ノックアウト反応,多核子剥離反応,陽子非弾性散乱と$$gamma$$線分光によって調査した。すでに知られていた2つに加えて、3$$^{-}$$状態の候補を含む5つの状態を新たに確認した。$$gamma$$ $$gamma$$ coincidenceによって得られた準位図は$$sd-pf$$模型空間での殻模型計算やカイラル2体・3体力による第一原理計算と比較した。陽子・中性子ノックアウト反応断面積の理論との比較により、新たに発見された2つの状態は2$$^{+}$$状態であり、また以前に4$$^{+}_{1}$$とされていた状態も2$$^{+}$$であることが示唆された。


Extremely high dislocation density and deformation pathway of CrMnFeCoNi high entropy alloy at ultralow temperature

Naeem, M.*; He, H.*; Harjo, S.; 川崎 卓郎; Zhang, F.*; Wang, B.*; Lan, S.*; Wu, Z.*; Wu, Y.*; Lu, Z.*; et al.

Scripta Materialia, 188, p.21 - 25, 2020/11

The deformation behavior of CrMnFeCoNi high entropy alloy was investigated by in situ neutron diffraction at an ultralow temperature of 15 K. Analysis of the diffraction peak widths showed an extremely high dislocation density at 15 K, reaching $$sim$$10$$^{16}$$ m$$^{-2}$$. In addition, the dislocation density was found to closely follow the development of texture caused by deformation. In contrast to deformation by dislocation slip at room temperature, the ultralow-temperature deformation also involved stacking faults, twinning and serrations. The deformation pathway at ultralow temperature is outlined which is responsible for the extraordinary strength-ductility combination.


Distance-selected topochemical dehydro-diels-alder reaction of 1,4-Diphenylbutadiyne toward crystalline graphitic nanoribbons

Zhang, P.*; Tang, X.*; Wang, Y.*; Wang, X.*; Gao, D.*; Li, Y.*; Zheng, H.*; Wang, Y.*; Wang, X.*; Fu, R.*; et al.

Journal of the American Chemical Society, 142(41), p.17662 - 17669, 2020/10

 被引用回数:6 パーセンタイル:75.63(Chemistry, Multidisciplinary)



Comparison of dislocation density, twin fault probability, and stacking fault energy between CrCoNi and CrCoNiFe medium entropy alloys deformed at 293 and 140K

Woo, W.*; Naeem, M.*; Jeong, J.-S.*; Lee, C.-M.*; Harjo, S.; 川崎 卓郎; He, H.*; Wang, X.-L.*

Materials Science & Engineering A, 781, p.139224_1 - 139224_7, 2020/04

 被引用回数:6 パーセンタイル:76.25(Nanoscience & Nanotechnology)

To elucidate deformation behavior behind the exceptional mechanical properties of CrCoNi based medium entropy alloys, the deformation related microstructural parameters were determined by using in situ neutron diffraction and peaks profile analysis methods. Superior tensile strength and elongation of the CrCoNi alloy is relevant to higher twin fault probability ($$P_{tw}$$, up to 3.8%) and dislocation density ($$rho$$, up to 9.7 $$times$$ 10$$^{15}$$ m$$^{-2}$$) compared to those (1.3% and 3.4 $$times$$ 10$$^{15}$$ m$$^{-2}$$, respectively) of the CrCoNiFe at 293K. Meanwhile, at 140K, the $$P_{tw}$$ of the CrCoNiFe significantly increased up to 4.4% with the stable $$rho$$ of $$sim$$5.0 $$times$$ 10$$^{15}$$ m$$^{-2}$$ and its mechanical properties overwhelm those of the CrCoNi at 273K. Such twinning dominant deformation mechanism at low temperature is also assured by lower stacking fault energy (SFE) of the CrCoNiFe at 140K compared to those of the CrCoNi and CrCoNiFe alloys at 293K.


Shell structure of the neutron-rich isotopes $$^{69,71,73}$$Co

Lokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; 緒方 一介*; 吉田 数貴; Authelet, G.*; et al.

Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03

 被引用回数:4 パーセンタイル:79.36(Physics, Nuclear)

中性子過剰核である$$^{69,71,73}$$Coに対する($$p,2p$$)ノックアウト反応が理化学研究所RIBFで測定された。$$gamma-gamma$$ coincidenceの方法で準位構造が決定され、測定された包括的断面積および排他的断面積から暫定的ではあるがスピン・パリティが決定された。殻模型計算との比較により、$$^{69,71,73}$$Coの低励起状態には球形核と変形核が共存することが示唆された。

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