Spin-singlet ground state with spin gap in = antiferromagnetic tetramer compound YbSiO

長谷 正司*; 金子 耕士; 田端 千紘; 山内 宏樹; 辻井 直人*; Dnni, A.*

Physical Review B, 111(9), p.094403_1 - 094403_9, 2025/03

https://doi.org/10.1103/PhysRevB.111.094403

We studied magnetic properties of YbSiO having pseudospins of = using magnetization, specific heat, and inelastic neutron scattering (INS) measurements. We observed cluster-like excitations in the INS measurements. We determined that the spin system in YbSiO is the = AFM tetramer with two exchange interactions of and ~meV. The spin tetramer can explain the excitation energies, , magnetic specific heat at ~K, and the magnitude of the scattering vector () dependence of the intensity [] at 0.7 and 1.2 meV. The spin tetramer, however, cannot explain well at 1.9 meV and of the three excitations probably due to effects of weak inter-tetramer interactions.

Large spontaneous Hall effect with flexible domain control in the antiferromagnetic material TaMnP

小手川 恒*; 中村 彰良*; Huyen, V. T. N.*; 新井 祐樹*; 藤 秀樹*; 菅原 仁*; 林 純一*; 武田 圭生*; 田端 千紘; 金子 耕士; et al.

Physical Review B, 110(21), p.214417_1 - 214417_8, 2024/12

https://doi.org/10.1103/PhysRevB.110.214417

In this study, we show that the orthorhombic system TaMnP exhibits a large anomalous Hall conductivity (AHC) in spite of the small net magnetization. Neutron scattering experiment and the observation of the AH effect comprehensively suggest a dominant AF structure in TaMnP is represented by . The AHC is one of the largest among those observed in AF materials at zero fields. First-principles calculations suggest that the spin-orbit interaction originating in nonmagnetic Ta-5 electrons significantly contributes to the enhancement of Berry curvatures in the momentum space. We found that the AF domain switching is triggered by the magnetic fields along all the crystal axes. This indicates that the AF domain determining the sign of the Hall response can be controlled even through the small net magnetization symmetrically different.

Polarized neutron diffraction study on UPtSi

今 布咲子*; 田端 千紘; 齋藤 開*; 中島 多朗*; 日高 宏之*; 柳澤 達也*; 網塚 浩*

Journal of the Physical Society of Japan, 93(4), p.044701_1 - 044701_11, 2024/04

https://doi.org/10.7566/JPSJ.93.044701

We investigated the magnetic structure of the antiferromagnetic (AFM) ordered state ( 34 K) in tetragonal UPtSi using polarized and unpolarized neutron diffraction. Previous neutron scattering studies reported that this system possesses a simple AFM structure with a propagation vector, Q= 0, and the ordered magnetic moments aligned along the c-axis. By contrast, our latest resonant X-ray scattering (RXS) experiments have revealed that the magnetic structure is modulated by the charge-density-wave (CDW) order, which emerges in one of the two Pt atomic layers in the unit cell below 320 K. The modulation is characterized by a transverse wave in the c-plane, with the propagation vector of the CDW order, q = (0.42, 0, 0). In this study using neutron scattering, we observed that the superlattice reflections specified by q develop below , in addition to the magnetic reflections with Q= 0, thereby further confirming the presence of modulation in the AFM structure of this system. From detailed analyses, we revealed that the amplitude of the transverse-wave magnetic modulation is 0.72(2)/U, which is quantitative information that can not be obtained through RXS experiments. This implies that the CDW drives the ordered magnetic moments to be tilted up to 20 in the AFM state. The observations strongly suggest that the magnetism of UPtSi is heavily influenced by the hybridization effects between the electrons of U and the 5d electrons of Pt.

New standard for low temperature sample environment at JAEA/JRR-3

金子 耕士; 田端 千紘; 萩原 雅人; 山内 宏樹; 大場 洋次郎; 熊田 高之; 久保田 正人; 児島 佑樹*; 生田目 望; 佐々木 未来; et al.

JPS Conference Proceedings (Internet), 41, p.011015_1 - 011015_6, 2024/03

https://doi.org/10.7566/JPSCP.41.011015

We will introduce our recent update on low temperature system for neutron diffraction experiments. This is characterized by advantages such as liquid He free and sophisticated automatic temperature control functions, which can be a new standard for low temperature and high magnetic field experiments of neutron scattering.

Incommensurate nature of the antiferromagnetic order in GdCu

金子 耕士; 田端 千紘; 萩原 雅人; 山内 宏樹; 久保田 正人; 長壁 豊隆; 大貫 惇睦*

Journal of the Physical Society of Japan, 92(8), p.085001_1 - 085001_2, 2023/08

https://doi.org/10.7566/JPSJ.92.085001

A magnetic order in orthorhombic GdCu was investigated by a single crystal neutron diffraction with thermal neutron. Magnetic peaks were observed at incommensurate positions described by the ordering vector =(~1~0) with =0.678 at 4~K. This ordering vector is close to the commensurate one with =(2/3~1~0) reported earlier, but clearly deviates. The incommensurate nature of the magnetic order in GdCu is further corroborated by the peak shift with temperature below .

Influence of additives on low-temperature hydrothermal synthesis of UO and ThO

田端 千紘; 白崎 謙次*; 酒井 宏典; 砂賀 彩光*; Li, D.*; 小中 真理子*; 山村 朝雄*

CrystEngComm (Internet), 24(19), p.3637 - 3648, 2022/05

https://doi.org/10.1039/D2CE00278G

Hydrothermal reactions of uranium(IV) nitrate solutions in the presence of aldehydes yielded microparticles of UO, at temperatures as low as 100C. The synthesized products contained residual organic matter originating from aldehydes used as an additive, unless the synthesis temperature was 390C. Additionally, the residual matter could be separated from the product by heat treatment at 300C. The valence of uranium ions in the UO products was found to be higher than that reported for UO. Low synthesis temperatures resulted in the suppression of the magnetic moments of uranium ions and the occurrence of the spin interaction among the ions. Therefore, the oxidation number of uranium averaged over the entire product could become higher than 4+. A comparative study with ThO suggested that the redox reaction could be closely related to the hydrothermal synthesis reaction and particle growth of UO.

Supercritical hydrothermal synthesis of UO; Stoichiometry, crystal shape and size, and homogeneity observed using Na-NMR spectroscopy of (U, Na)O

田端 千紘*; 白崎 謙次*; 砂賀 彩光*; 酒井 宏典; Li, D.*; 小中 真理子*; 山村 朝雄*

CrystEngComm (Internet), 23(48), p.8660 - 8672, 2021/12

https://doi.org/10.1039/D1CE00996F

超臨界水下においてウラン酸化物UOの水熱合成について調べた。得られたUO粒子について、その化学組成,結晶形,サイズ,均一性などを調べた結果、超臨界水熱合成法は、化学的に制御された均一なUOを合成するのに有効である可能性がある。

X-ray backscattering study of crystal lattice distortion in hidden order of URuSi

田端 千紘*; 稲見 俊哉; 道村 真司*; 横山 淳*; 日高 宏之*; 柳澤 達也*; 網塚 浩*

Philosophical Magazine, 94(32-33), p.3691 - 3701, 2014/00

https://doi.org/10.1080/14786435.2014.952701

We performed synchrotron X-ray diffraction measurements on a small single crystal of URuSi. A backscattering diffraction setup (2) in combination with a Si(6 6 0) monochromator ensures a high instrumental resolution of , where denotes a lattice-plane spacing and is its spread expressed as the full width at half maximum (FWHM). We carefully measured the (5 5 0) Bragg peak in the temperature range between 5 and 25 K, and found it to show no signature of broadening and splitting when "Hidden Order (HO)" sets in below 17.5 K. Temperature variation of the peak position closely follows the behaviour of the known linear thermal expansion coefficient. Detailed analysis of the peak width reveals that the tetragonal fourfold rotational symmetry of URuSi is conserved in HO within the experimental accuracy of the orthorhombicity of .

JMTR改良LEU炉心の核特性解析

小向 文作; 那珂 通裕; 田畑 俊夫; 長尾 美春; 武田 卓士*; 藤木 和男

JAERI-Tech 2002-067, 75 Pages, 2002/08

JAERI-Tech-2002-067.pdf:3.41MB

JMTRでは、燃料の燃焼度を増加させてより有効に利用することによって運転日数を大幅に増加させる検討を行った結果、従来のLEU炉心に対して標準燃料要素を新たに2体追加して燃料要素29体で構成された改良LEU炉心を考案した。本炉心の核特性をSRACコードシステムを用いて解析した結果、LEU炉心と比べて運転サイクル開始時の過剰反応度が若干大きくなるなどの違いはあるものの、JMTRの安全設計における核特性の設計方針を満足することを確認した。また、本炉心では1サイクル当たり最長32日までの運転が可能であり、燃料要素平均の燃焼度を最高約54%まで増加できることから、従来の4サイクル分の燃料要素消費数で年間180日以上の運転が可能なことがわかった。

Resonant X-ray scattering study of the nonmagnetic order of 5f electrons in a pseudo-Kagome layered system URhSn

田端 千紘; 今 布咲子*; 網塚 浩*; 清水 悠晴*; 青木 大*; 中尾 裕則*

no journal, , 

Magnetic materials with no inversion center at the magnetic site have attracted much attention from the viewpoints of chiral magnetic orders and electromagnetic effects in recent years. URhSn has a crystal structure without spatial inversion symmetry (hexagonal, space group P-62m) consisting of distorted Kagome layers, and according to previous reports on polycrystalline samples, it undergoes a two-step phase transition at To = 54 K and TC = 16 K. While the low-temperature phase is considered a ferromagnetic phase with spontaneous magnetization along the c-axis, the order parameter of the high-temperature phase has remained unknown for decades. No symmetry breaking has been detected for this mysterious phase by microscopic measurements such as powder neutron diffraction and Mossbauer spectroscopy. We recently succeeded in growing high-quality single crystals of this compound and clarified its detailed bulk properties (specific heat, magnetization, electrical resistivity, and thermal expansion). Interestingly, the high-temperature phase below To isstabilized by a magnetic field parallel to the c-axis, despite the absence of a c-axis spontaneous magnetization component. This peculiar behavior indicates neither a simple ferromagnetic nor antiferromagnetic scenario. We investigated the order parameter of this unknown phase using a resonant X-ray scattering (RXS) technique. On the resonance condition at the M4 absorption edge of U, we observed a slight increase in the intensity of a fundamental Bragg reflection below To, suggesting an order parameter with q = 0 that does not break the translational symmetry of the crystal. The observed RXS signal can be interpreted by either case of order parameters of magnetic dipoles and electric quadrupoles. Given the Sn-Mossbauer and Sn-NMR reports of no internal magnetic field associated with the order, an electric quadrupolar order is more plausible.