First observation of O

近藤 洋介*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; 馬場 秀忠*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.

Nature, 620(7976), p.965 - 970, 2023/08

https://doi.org/10.1038/s41586-023-06352-6

非常に中性子が過剰な原子核Oは、陽子、中性子ともに魔法数であることから古くからその性質に興味が持たれていたが、酸素の最後の束縛核Oよりも中性子が4個も多いため、これまで観測されてこなかった。この論文では、理化学研究所RIBFにてFからの1陽子ノックアウト反応によってOを生成し、そこから放出される中性子を測定することによって初めてその観測に成功した。核構造の観点からは、Oでは二重閉殻が保たれているか興味が持たれていたが、実験で得られた分光学的因子が殻模型計算で予言されて程度の大きいことから、閉殻構造をもたない可能性が高いことがわかった。

垂直磁気異方性を示す鉄挿入遷移金属ダイカルコゲナイドFeTaSのX線磁気円二色性による研究; FeTiSとの比較

芝田 悟朗; Won, C.*; Kim, J.*; 野中 洋亮*; 池田 啓祐*; Wan, Y.*; 鈴木 雅弘*; 小出 常晴*; 田中 新*; Cheong, S.-W.*; et al.

Photon Factory Activity Report 2022 (インターネット), 2 Pages, 2023/00

https://pfwww.kek.jp/acr/2022pdf/u_reports.html

Feをインターカレートした遷移金属ダイカルコゲナイド化合物FeTiSおよびFeTaSは、巨大な保磁力および垂直磁気異方性を示す強磁性体になることが知られている。我々は以前、FeTiSについてのX線磁気円二色性(XMCD)実験の結果から、Feの凍結していない軌道磁気モーメントが結晶場の1次摂動によって直接磁気異方性エネルギーを生むことを明らかにした。今回、FeTiSよりもさらに強い磁気異方性を示す遷移金属ダイカルコゲナイドFeTaSについて同様にXMCD実験を行い、磁気異方性の強さが何によって左右されているかを探ることを試みた。

Repeatable photoinduced insulator-to-metal transition in yttrium oxyhydride epitaxial thin films

小松 遊矢*; 清水 亮太*; 佐藤 龍平*; Wilde, M.*; 西尾 和記*; 片瀬 貴義*; 松村 大樹; 齋藤 寛之*; 宮内 雅浩*; Adelman, J. R.*; et al.

Chemistry of Materials, 34(8), p.3616 - 3623, 2022/04

https://doi.org/10.1021/acs.chemmater.1c03450

Here, we demonstrate such a highly repeatable photoinduced insulator-to-metal transition in yttrium oxyhydride (YOH) epitaxial thin films. The temperature () dependence of the electrical resistivity () of the films transforms from insulating to metallic () under ultraviolet laser illumination. The sample is heated (125 C) under an Ar atmosphere to recover its original insulating state. The films recover their original metallic conductivity when subsequently subjected to ultraviolet laser illumination, showing repeatable photoinduced insulator-to-metal transition. First principles calculations show that the itinerant carriers originate from the variations in the charge states of the hydrogen atoms that occupy octahedral interstitial sites. This study indicates that tuning the site occupancy (octahedral/tetrahedral) of the hydrogen atoms exerts a significant effect on the photoresponse of metal hydrides.

Triplon current generation in solids

Chen, Y.*; 佐藤 正寛*; Tang, Y.*; 塩見 雄毅*; 大柳 洸一*; 益田 隆嗣*; 南部 雄亮*; 藤田 全基*; 齊藤 英治

Nature Communications (Internet), 12, p.5199_1 - 5199_7, 2021/08

https://doi.org/10.1038/s41467-021-25494-7

A triplon refers to a fictitious particle that carries angular momentum corresponding to the elementary excitation in a broad class of quantum dimerized spin systems. Such systems without magnetic order have long been studied as a testing ground for quantum properties of spins. Although triplons have been found to play a central role in thermal and magnetic properties in dimerized magnets with singlet correlation, a spin angular momentum flow carried by triplons, a triplon current, has not been detected yet. Here we report spin Seebeck effects induced by a triplon current: triplon spin Seebeck effect, using a spin-Peierls system CuGeO. The result shows that the heating-driven triplon transport induces spin current whose sign is positive, opposite to the spin-wave cases in magnets. The triplon spin Seebeck effect persists far below the spin-Peierls transition temperature, being consistent with a theoretical calculation for triplon spin Seebeck effects.

Magnon pairs and spin-nematic correlation in the spin Seebeck effect

廣部 大地*; 佐藤 正寛*; 萩原 雅人*; 塩見 雄毅*; 益田 隆嗣*; 齊藤 英治

Physical Review Letters, 123(11), p.117202_1 - 117202_7, 2019/09

https://doi.org/10.1103/PhysRevLett.123.117202

Investigating exotic magnetic materials with spintronic techniques is effective at advancing magnetism as well as spintronics. In this work, we report unusual field-induced suppression of the spin Seebeck effect (SSE) in a quasi-one-dimensional frustrated spin- magnet LiCuVO, known to exhibit spin-nematic correlation in a wide range of external magnetic field . The suppression takes place above T in spite of the -linear isothermal magnetization curves in the same range. The result can be attributed to the growth of the spin-nematic correlation while increasing . The correlation stabilizes magnon pairs carrying spin 2, thereby suppressing the interfacial spin injection of SSE by preventing the spin-1 exchange between single magnons and conduction electrons at the interface. This interpretation is supported by integrating thermodynamic measurements and theoretical analysis on the SSE.

One-dimensional spinon spin currents

廣部 大地*; 佐藤 正寛*; 川股 隆行*; 塩見 雄毅*; 内田 健一*; 井口 亮*; 小池 洋二*; 前川 禎通; 齊藤 英治

Nature Physics, 13(1), p.30 - 34, 2017/01

https://doi.org/10.1038/nphys3895

Quantum spin fluctuation in a low-dimensional or frustrated magnet breaks magnetic ordering while keeping spin correlation. Such fluctuation has been a central topic in magnetism because of its relevance to high-Tc superconductivity and topological states. However, utilizing such spin states has been quite difficult. In a one-dimensional spin-1/2 chain, a particle-like excitation called a spinon is known to be responsible for spin fluctuation in a paramagnetic state. Spinons behave as a Tomonaga-Luttinger liquid at low energy, and the spin system is often called a quantum spin chain. Here we show that a quantum spin chain generates and carries spin current, which is attributed to spinon spin current. This is demonstrated by observing an anisotropic negative spin Seebeck effect along the spin chains in SrCuO. The results show that spin current can flow even in an atomic channel owing to long-range spin fluctuation.

Silicon avalanche photodiode linear-array detector with multichannel scaling system for pulsed synchrotron X-ray experiments

岸本 俊二*; 三井 隆也; 春木 理恵*; 依田 芳卓*; 谷口 敬*; 島崎 昇一*; 池野 正弘*; 斉藤 正俊*; 田中 真伸*

Journal of Instrumentation (Internet), 10(5), p.C05030_1 - C05030_6, 2015/05

https://doi.org/10.1088/1748-0221/10/05/C05030

We developed an X-ray detector system using a 64-pixel silicon avalanche photodiode Si-APD linear array and fast pulse-counting electronics for multichannel scaling. The Si-APD linear array consists of 64 pixels each 0.010.02 cm in size, with a pixel pitch of 0.015 cm and depletion depth of 0.001 cm. The fast electronics, consisting of an ultrafast application-specific integrated circuit and field-programmable gate arrays, can record both the position and timing of X-rays arriving at each pixel of the linear array with 1 ns pulse-pair resolution. The count distribution was measured using 14.4 keV synchrotron X-rays for nuclear resonant forward scattering experiments on Fe, and the spatial resolution was improved by inclining the detector. We also successfully measured amorphous alloy FeSiB during heating.

原子力緊急時支援・研修センターの活動(平成25年度)

佐藤 猛; 武藤 重男; 秋山 聖光; 青木 一史; 岡本 明子; 川上 剛; 久米 伸英; 中西 千佳; 小家 雅博; 川又 宏之; et al.

JAEA-Review 2014-048, 69 Pages, 2015/02

JAEA-Review-2014-048.pdf:13.91MB

日本原子力研究開発機構は、災害対策基本法及び武力攻撃事態対処法に基づき、「指定公共機関」として、国及び地方公共団体その他の機関に対し、災害対策又は武力攻撃事態等への対処において、原子力機構の防災業務計画及び国民保護業務計画に則り、技術支援をする責務を有している。原子力緊急時支援・研修センターは、緊急時には、全国を視野に入れた専門家の派遣、防災資機材の提供、防護対策のための技術的助言等の支援活動を行う。また、平常時には、我が国の防災対応体制強化・充実のために、自らの訓練・研修のほか、国、地方公共団体、警察、消防、自衛隊等の原子力防災関係者のための実践的な訓練・研修、原子力防災に関する調査研究及び国際協力を実施する。平成25年度においては、原子力機構の年度計画に基づき、以下の業務を推進した。(1)国, 地方公共団体等との連携を図った指定公共機関としての技術支援活動、(2)国, 地方公共団体等の原子力防災関係者の人材育成及び研修・訓練、(3)原子力防災に係る調査・研究の実施及び情報発信、(4)国際機関と連携を図ったアジア諸国への原子力防災に係る国際貢献。また、指定公共機関としてこれまでに培った経験及び福島事故への初動時からの対応等を活かし、国レベルでの防災対応基盤の強化に向け、専門家として技術的な支援を行うとともに、支援・研修センターの機能の維持・運営及び国との連携を図った自らの対応能力強化などに重点的に取り組んだ。

Effect of hydrogen on crack growth behavior in F82H steel using small-size specimen

伊藤 譲; 齋藤 正博*; 阿部 勝憲*; 若井 栄一

Small Specimen Test Techniques; 6th Volume (ASTM STP 1576), p.209 - 224, 2015/00

Crack growth is a one of the key mechanical properties of the design evaluation in fusion materials to be tested at the High Flux Test Module (HFTM) in IFMIF. In the IFMIF/EVEDA project under the BA agreement, effect of hydrogen on the crack growth in F82H steel was investigated by using the relatively small size specimen. The shape of an Wedge Opening Load (WOL) specimen is adapted as a miniaturized specimen because the loading mechanism of WOL specimen is relatively simple compared to that of the other notched specimen. The hydrogen charging process was conducted for about 600 hours in the electrolytic solution with the current density of -2 mA/cm at 35C. And then, the testing load, = 30 MPa, was applied to the specimen for about 337 hours at room temperature in air as the crack growth rate test. From these results, the small size specimen used in this study is thought to be adequate to evaluate the effect of hydrogen on the crack behavior in F82H steel.

Influence of electron doping on magnetic order in CeRuAl

小林 理気*; 金子 耕士; 斉藤 耕太郎*; Mignot, J.-M.*; Andr, G.*; Robert, J.*; 脇本 秀一; 松田 雅昌*; Chi, S.*; 芳賀 芳範; et al.

Journal of the Physical Society of Japan, 83(10), p.104707_1 - 104707_5, 2014/10

https://doi.org/10.7566/JPSJ.83.104707

The effect of electron doping by the substitution of Rh for Ru on unconventional magnetic order in CeRuAl was investigated via neutron powder diffraction. In Ce(RuRh)Al with = 0.05, 0.12, 0.2, reorientation of the ordered moment from the - to the -axis takes place in all samples, while the ordering vector = (0 1 0) remains unchanged within this concentration range. The moment reorientation is accompanied by an enhancement in its size by a factor of 2.4, from =0.43 at = 0 to =1.06, 1.04, and 1.02 for = 0.05, 0.12 and 0.2, respectively. The continuous decrease in Nel temperature (), despite an abrupt increase in , underlines the strong anisotropy in the exchange interaction in CeRuAl, and the fact that this anisotropy is easily suppressed by electron doping.