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Fe
O
森 道康; Tomasello, B.*; Ziman, T.*
no journal, ,
The spin Seebeck effect is a phenomenon of thermoelectric generation that occurs in a device consisting of a bilayer of a metal and a ferromagnet. When ferrimagnetic TbFeO (TbIG) is substituted for the ferromagnet, the effect goes to zero at low temperatures, yet it increases to positive values by applying a magnetic field. This is opposite to the expectation that the SSE should be suppressed by a magnetic field due to the increase in the magnon gap. In this talk, the crystal-field excitations (CFE) in TbIG are calculated within a mean field theory using the Stevens parameters of TbGaO (TGG) obtained by the neutron-scattering experiment. The primitive cell of TbIG hosts twelve Tb sites with six inequivalent magnetic sublattices, but due to the net [111] molecular field from the tetrahedral and octahedral Fe ions, these can be classified into two distinct groups, the C and the C' sites, which account for the double umbrella magnetic structure. We show that when an external magnetic field is applied along the [111] direction of the crystal, the lowest CFE of the C sublattices decreases. As a consequence of the magnetic field dependence of the lowest CFE, we find that at low temperatures the SSE in TbIG can be enhanced by an applied magnetic field.
Micheau, C.; 元川 竜平; 上田 祐生; Bourgeois, D.*; Simonnet, M.*
no journal, ,
Solvent extraction efficiency relies on the metal affinity for extractant complexing part, and extractant aggregate structures. It was recently demonstrated that aggregates contribute to metal size recognition in the bulk impacting the selectivity, while the abundance of extractant/aggregates at the interface contribute to metal transfer in the organic phase impacting extraction kinetics. However, finely adjust the structures formed in the organic phase remain a challenge as the factors influencing their formation are not clearly defined. As the size recognition effect for the separation of Pd(II) and Nd(III) was initially observed using N,N-dibutyl-N,N-dimethyl-2-tetradecylmalonamide extractant (DBMA) in toluene and heptane, it has been decided to investigate mixtures of these two solvents at different volume ratios. Extractant aggregate size in these mixtures contacted to different nitric acid solution was determined using SANS at JRR-3 (Tokai, Japan), and correlated to selectivity coefficients determined using ICP-OES. From the SANS data analysis, three main factors influencing aggregate size have been pointed out: (i) acidity of aqueous phase, (ii) extraction of nitrate ions, and (iii) relative permittivity of the diluent. In this way, bigger aggregates were obtained in heptane contacted to 5M HNO
(RG = 4.44 nm), whereas the smallest ones were obtained in toluene contacted to 1M HNO (RG = 0.53 nm), with effects (i) and (ii) becoming more pronounced as the permittivity decreases. Finally, selectivity coefficients were shown to continuously decrease as the size of the aggregate increases. In this study it is demonstrated that the size of the aggregate is directly correlated to the selectivity coefficient which is maximum for small aggregates. In this way selectivity can be finely tuned adjusting either the organic phase or the aqueous phase composition. In a future work, external stimuli will be applied to tune the selectivity on unique chemical systems.
川崎 卓郎; Gong, W.; 伊東 達矢; 相澤 一也; Harjo, S.
no journal, ,
The Engineering Materials Diffractometer (TAKUMI) at the J-PARC MLF is a powerful tool for investigating the relationship between the mechanical properties and structure of engineering materials, such as steels, light metals, and alloys. A primary technique employed at TAKUMI involves in-situ neutron diffraction measurements during deformation tests. By correlating applied stress and strain with changes in lattice strain, texture, phase transformation, and dislocation density, researchers can elucidate the underlying mechanisms governing material strength and ductility. To enhance these studies, a suite of equipment is available, including deformation testing machines, temperature control systems, electric field generators, Euler cradles for texture analysis, and acoustic emission and thermography systems for concurrent property evaluation. At TAKUMI, to meet the growing demand for materials with superior mechanical properties at low temperatures for hydrogen energy applications, we have developed a low-temperature deformation testing system combined with digital image correlation for in-situ neutron diffraction experiments. This system enables precise measurement of deformation and strain localization in materials at cryogenic temperatures. This presentation will highlight the capabilities of this system and introduce other sample environment equipment available at J-PARC MLF for engineering materials research.
Harjo, S.; 川崎 卓郎; Gong, W.
no journal, ,
Steels have long been key structural materials, with ongoing development to meet modern demands. Neutron diffraction, used for over three decades, initially focused on residual stress measurement. Advancements in spallation sources now enable quantitative analysis of microstructure evolution. We have developed devices and methods for operando experiments under various thermal and mechanical conditions. The presentation covers heat-treatment effects in high-strength steels, impact of hydrogen on 310S steel, and cryogenic deformation of ultrafine-grained 304 steel.
廣井 孝介; 林田 洋寿*; 篠原 武尚
no journal, ,
Small-angle neutron scattering (SANS) is a neutron scattering technique that is widely used for analyzing hierarchical structures inside materials. To obtain structural information whose size is larger than several hundred nm, ultra-small-angle neutron scattering (USANS) measurement is required in which incident neutron beam is highly collimated, and thus, greatly loss the incident neutron flux. This loss of incident flux results in long measurement time, which is a major obstacle to applying USANS method to various fields of material science. Recently, spin-echo modulated small-angle neutron scattering (SEM-SANS) has attracted attention as a method to obtain USANS information efficiently. To realize SEM-SANS experiments at MLF, we constructed SEM-SANS experimental setup at BL22 RADEN. In this presentation, we will show details of our experimental setup and some results of demonstration studies.
中部 倫太郎; 熊田 高之; 元川 竜平
no journal, ,
細胞の凍結保存には、氷結晶の成長に伴う細胞組織の物理的損傷を防ぐことが重要である。そのために凍結防止剤として糖を添加し、急速凍結によりガラス化させることによって氷結晶の生成と成長を抑制している。一般的に、氷結晶の大きさが1
m以下に留まれば細胞小器官に影響を与えないと考えられている。したがって、糖の種類、濃度に依存した氷結晶の大きさと形状が観測できれば、細胞生存率の高い凍結保存法の確立につながる。通常のSANS法では、糖が偏析したアモルファスと氷結晶の間の散乱長密度(SLD)差が小さいゆえに、アモルファス中に含まれる欠陥構造との弁別ができなかった。対して我々は、偏極水素核と偏極中性子の干渉性散乱長が互いの偏極度の積に依存して変化する原理を利用したスピンコントラスト変調中性子小角散乱(SCV-SANS)法を、1m以下の氷結晶を観測する手法として適用した。J-PARCのSANSビームライン(TAIKAN)でのSCV-SANS測定から、我々は凍結グルコース水溶液中の氷結晶が高さ数nmの平板形状であることを決定した。本講演では、その詳細な実験手法とこの氷結晶の形状が示唆する物理的な背景、そして、高圧という新たな指標を取り入れた今後のSCV-SANS測定について報告する。
大原 高志; 鬼柳 亮嗣; 中尾 朗子*; 宗像 孝司*; 石川 喜久*; 森山 健太郎*
no journal, ,
In structure analysis of molecular crystals, single-crystal neutron diffraction is a powerful technique that can reliably observe molecular structures, including hydrogen atoms. However, it requires a large single-crystal, and consequently, the measurement time is often insufficient for the sample size. On the other hand, the structural information of non-hydrogen atoms is usually determined with high accuracy by single-crystal X-ray diffraction. Therefore, in some cases, it is still acceptable if structural information regarding only the hydrogen atoms of interest can be obtained from neutron diffraction data with accuracy in line with the research objectives, even when the measurement time is not enough for the full-matrix refinement. In this study, we generated pseudo-short-measurement-time diffraction data from raw diffraction data measured with a single-crystal diffractometer SENJU in MLF. Subsequently, we evaluated the structural parameters of hydrogen atoms obtained from these data with structural information obtained by X-ray diffraction.
鬼柳 亮嗣; 大原 高志; 石川 喜久*; 宗像 孝司*; 森山 健太郎*; 中尾 朗子*; 中村 龍也; 藤 健太郎; 坂佐井 馨; 細谷 孝明
no journal, ,
SENJU is a time-of-flight (TOF) single-crystal neutron diffractometer designed for precise analyses of crystal and magnetic structure under diverse sample environments, including low temperatures, high pressures, and magnetic fields. It can measure small samples as small as 0.1 mm. SENJU features extensive detector coverage enabled by 36 detectors, each with a sensitive area of 256 
256 mm. These detectors are grouped into modules, with three detectors stacked vertically to form one module. A total of 12 such modules are arranged in a circular configuration around the vacuum sample chamber at the center of the instrument. This arrangement, combined with the white neutron beam provided by MLF, enables efficient measurements in three-dimensional reciprocal space. However, gaps between adjacent detectors reduce measurement efficiency and can complicate data acquisition. To address these limitations and enhance measurement efficiency, a novel "fan-like detector arrangement" has been developed using newly designed, larger detectors with dimensions of 512 768 mm, six times larger than the original detectors. These new detectors feature an asymmetric frame design around the sensitive area, where one edge of the frame is narrower than the others. The new detectors will be arranged in a circular configuration similar to the original setup but positioned such that adjacent detectors overlap slightly, with the narrower frame positioned in front of the neighboring detector. This arrangement effectively eliminates the gaps between detectors through appropriate data processing, enabling more efficient and seamless measurements. The replacement process has recently commenced, involving the substitution of the existing nine detectors with two newly designed detectors. The complete transition is anticipated to require several years to finalize. This upgraded system is expected to significantly enhance the efficiency and effectiveness of data collection, providing improved performance and reliability for experimental operations.
鬼柳 亮嗣; 大原 高志; 石川 喜久*; 宗像 孝司*; 森山 健太郎*; 中尾 朗子*
no journal, ,
SENJU, a time-of-flight (TOF) single-crystal neutron diffractometer at MLF in J-PARC, has been operational since 2012. Single-crystal neutron diffraction is a powerful technique for determining precise crystal and magnetic structures, attracting numerous users to SENJU. However, compared to powder diffraction, the data-handling process for single-crystal diffraction is significantly more complex. This complexity often discourages new users and imposes a substantial burden on the instrument staff, who must provide extensive support to ensure successful experiments. To address these challenges, efforts have been dedicated to improving the usability of SENJU's experimental workflow and data processing protocol. The first step in single-crystal diffraction data analysis is determining the orientation of the sample crystal. Without this information, the position in reciprocal space cannot be identified, nor can reflections be indexed. The crystal orientation is described by the UB matrix, which relates the crystal orientation to the instrument's coordinate system. However, determining this matrix can be time-consuming. To streamline this process, a semi-automatic UB matrix determination program was developed based on the two-Bragg method. Once the UB matrix is established, reflections are measured for structure analysis. Given that datasets often exceed 10,000 reflections, manual verification of data reliability is impractical. To address this, a machine-learning-based system was developed to automatically identify and exclude unreliable data, ensuring robust datasets for subsequent analyses. In the context of structural or magnetic phase transitions, detecting and locating superlattice reflections is another key function of single-crystal diffraction. Exploring three-dimensional reciprocal space for such reflections is challenging; therefore, image recognition techniques were integrated to automate their detection, significantly simplifying this process. These advancements in SENJU's data-handling protocols have reduced operational complexities and enhanced user accessibility. Continuous optimization of such systems is vital to maintaining efficiency at user facilities like MLF.
柴崎 千枝; 奥 隆之; 他5名*
no journal, ,
日本の大強度陽子加速器施設(J-PARC)の物質・生命科学実験施設(MLF)では、中性子ビームを用いた物質科学・生命科学研究の数多くの実験が行われている。中性子散乱研究においては、局所的な情報の抽出、コントラスト変化散乱実験、あるいは水素由来の非干渉性散乱の抑制のために、重水素化試料が広く利用されている。しかし、日本国内における重水(D
O)の価格は過去10年間で数倍に高騰しており、安価に高濃度の純重水を得るための新たなリサイクル手法の開発が必要となっている。本研究では、微生物培養で発生する廃重水を対象に、不純物を蒸留および活性炭処理で除去した後、電気分解によって重水素濃度を高めることで、DOのリサイクル法を確立した。その結果、3Lの使用済みDO(96.6%)溶液から、1Lの再生DO(98.8%)を得ることに成功した。純度は31Pおよび1H NMR分光により確認され、不純物は検出されなかった。再生DOは、白金担持炭素触媒と2-プロパノールを用いたグリシンの重水素化においても阻害効果を示さず、有効に利用できた。さらに、複数種のアミノ酸についても同様の重水素化実験を行い、高い重水素化率を有するアミノ酸を得ることに成功した。このアプローチにより、DOのコスト削減と持続的な再利用が可能となる。今後は、アラニンやヒスチジンのような側鎖をもつアミノ酸の完全重水素化法を開発し、得られた重水素化ペプチドの機能的特性を探求していく予定である。