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中島 多朗*; 齋藤 開*; 小林 尚暉*; 川崎 卓郎; 中村 龍也; 古川 はづき*; 浅井 晋一郎*; 益田 隆嗣*
Journal of the Physical Society of Japan, 93(9), p.091002_1 - 091002_5, 2024/09
被引用回数：0Neutron scattering is a powerful tool to study magnetic structures and cross-correlated phenomena originated from symmetry of the magnetic structures in matter. Among a number of neutron scattering techniques, polarized neutron scattering is quite sensitive to the orientations of the magnetic moments, which are essential to understand microscopic mechanisms of the spin-driven emergent phenomena. Here, we present POlarized Neutron Triple-Axis spectrometer PONTA in the Japan Research Reactor 3 (JRR-3), and show the present capabilities of polarized and unpolarized neutron scattering by introducing recent results from the instrument.
寺田 典樹*; Khalyavin, D. D.*; Manuel, P.*; 浅井 晋一郎*; 益田 隆嗣*; 齋藤 開*; 中島 多朗*; 長壁 豊隆
Physical Review B, 110(2), p.024406_1 - 024406_9, 2024/07
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)フラストレート反強磁性体CuFeOは、圧力により、コメンシュレートなコリニアー相(CM1)からいくつかのインコメンシュレートでノンコリニアーな相への複雑な磁気相転移を示す。圧力が磁気相互作用に及ぼす影響を調べるために、高圧下で中性子回折および非弾性中性子散乱実験を行った。圧力が増すと、CM1基底状態は臨界圧力(
3GPa)以下でも磁場の印加に対して不安定になる。これは、2.1GPaで臨界磁場
が7.5Tから4.5Tに大幅に減少したことで確かめられた。さらに、スピン波分散関係のエネルギーギャップは、
=2.1GPaの圧力印加によって1.0meVから0.88meVに減少する。実験結果をスピン波計算と比較すると、スピン波励起の変化は、一軸異方性項または最近接交換相互作用の分離度のいずれかの減少によって説明できることがわかった。
池田 一貴*; 佐次田 頌*; 大友 季哉*; 大下 英敏*; 本田 孝志*; 羽合 孝文*; 齋藤 開*; 伊藤 晋一*; 横尾 哲也*; 榊 浩司*; et al.
International Journal of Hydrogen Energy, 51(Part A), p.79 - 87, 2024/01
被引用回数：3 パーセンタイル：43.34(Chemistry, Physical)Low-vanadium-concentration alloys have low durability, and their hydrogen absorption and desorption amounts decrease by 20% after 100 cycles. In this study, we conducted reverse Monte Carlo modeling on X-ray diffraction patterns and neutron pair distribution functions of the hydrogen-absorbed and desorbed samples of a V
Ti
Cr
alloy to analyze the variations in the local structure. The local structure surrounding the hydrogen atom in the hydrogen-absorbed phase exhibited minimal changes. In contrast, hydrogen occupied both tetrahedral and octahedral sites of the hydrogen-desorbed phase almost equally during the early cycles; however, the amount of hydrogen occupying the tetrahedral sites increased with the number of cycles.
高木 寛貴*; 高木 里奈*; 見波 将*; 野本 拓也*; 大石 一城*; 鈴木 通人*; 柳 有起*; 平山 元昭*; Khanh, N.*; 軽部 皓介*; et al.
Nature Physics, 19(7), p.961 - 968, 2023/07
被引用回数：30 パーセンタイル：98.48(Physics, Multidisciplinary)In ferromagnets, electric current generally induces a transverse Hall voltage in proportion to the internal magnetization. This effect is frequently used for electrical readout of the spin up and down states. While these properties are usually not expected in antiferromagnets, recent theoretical studies predicted that non-coplanar antiferromagnetic order with finite scalar spin chirality - meaning a solid angle spanned by neighboring spins - can induce a large spontaneous Hall effect even without net magnetization or external magnetic field. This phenomenon, the spontaneous topological Hall effect, can potentially be used for the efficient electrical readout of the antiferromagnetic states, but it has not been experimentally verified due to a lack of appropriate materials hosting such magnetism. Here, we report the discovery of all-in-all-out type non-coplanar antiferromagnetic order in triangular lattice compounds CoTa
S
and CoNbS. These compounds are reported to host unconventionally large spontaneous Hall effect despite their vanishingly small net magnetization, and our analysis reveals that it can be explained in terms of the topological Hall effect that originates from the fictitious magnetic field associated with scalar spin chirality. These results indicate that the scalar spin chirality mechanism offers a promising route to the realisation of giant spontaneous Hall response even in compensated antiferromagnets, and highlight intercalated van der Waals magnets as a promising quasi-two-dimensional material platform to enable various nontrivial ways of electrical reading and possible writing of non-coplanar antiferromagnetic domains.
高木 里奈*; 松山 直文*; Ukleev, V.*; Yu, L.*; White, J. S.*; Francoual, S.*; Mardegan, J. R. L.*; 速水 賢*; 齋藤 開*; 金子 耕士; et al.
Nature Communications (Internet), 13, p.1472_1 - 1472_7, 2022/03
被引用回数：76 パーセンタイル：99.47(Multidisciplinary Sciences)Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds. For the latter systems, a novel skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl
, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material.
MgGe with the Shastry-Sutherland lattice廣瀬 雄介; 本多 史憲*; 摂待 力生*; 中島 多朗*; 齋藤 開*
no journal, ,
Ce
MgGe crystallizes in the tetragonal MoFeB type structure, where Ce atoms form a frustrated arrangement, the Shastry-Sutherland lattice (SSL). The compound exhibits an antiferromagnetic ordering at TN=9.5 K and a complex magnetic phase diagram. To investigate the magnetic structure, we performed neutron scattering measurements on a single crystalline CeMgGe. A magnetic scattering, which grows below TN, is observed on a nuclear scattering, meaning that a magnetic propagation vector is zero. The spin-polarized neutron scattering experiment reveals that the magnetic moment of Ce atoms is aligned in the c plane. From the neutron scattering measurement, we determine the magnetic structure of CeMgGe with an ordered moment of about 1.5mB, which is almost consistent with the saturated magnetic moment.
尾関 和秀*; 米村 雅雄*; 増澤 徹*; 斎藤 秀俊*; 大越 康晴*; 平栗 健二*; 武田 全康
no journal, ,
DLC膜中の水素量は、DLC膜の機械的特性や膜そのものの微視的構造に大きく影響を与えるため、特性を制御したDLC膜を作成するために重要な因子である。本研究ではH/CH
比を変えながら、プラズマCVD法によりDLC膜を作成して、その水素量と膜密度の厚さ方向分布を中性子反射率法とX線反射率法を併用して求め、ERDAの結果と比較した。また、表面のO/Cの原子数比をXPSによって調べた。これらの結果を総合すると、水素存在量と膜密度は表面から深くなるにしたがって増加し、XPSの結果とも比較すると、表面の水素密度は膜の内部よりも小さいことが明らかになった。
の磁場誘起相探査への応用渡辺 真朗; 中島 多朗*; 稲村 泰弘; 松井 一樹*; 神田 朋希*; 野本 哲也*; 大石 一城*; 河村 幸彦*; 齋藤 開*; 玉造 博夢; et al.
no journal, ,
近年パルス磁場中での精密測定技術の進歩により、高磁場中での新奇な磁気状態が開拓されてきている。我々はスーパーキャパシタを用いて発生したロングパルス磁場とJ-PARCのパルス中性子を組み合わせることで、多波長中性子パルスが試料を通過する時間幅(約10ミリ秒)よりも十分長い磁場を試料位置で発生させ、14テスラまでの磁場下で定常磁場中実験と同様に逆格子空間を網羅的に探査できる測定環境を構築した。この手法をフラストレート磁性体CuFeOの磁気相転移の探査に適用した。
