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論文

Ductile-to-brittle transition in aluminum alloys

Zhou, D.*; Zhang, X.*; Pang, X.*; Zhao, Z.*; Chen, X.*; Wei, S.*; Yang, C.*; Gong, W.; Harjo, S.; Li, R.*; et al.

Materials Research Letters (Internet), 14(6), p.689 - 698, 2026/06

https://doi.org/10.1080/21663831.2026.2646271
 被引用回数：1 パーセンタイル：76.28(Materials Science, Multidisciplinary)

Here, we investigated the room-temperature (298 K) and cryogenic-temperature (77 K) mechanical behaviors of binary Al-Mg alloys over a wide range of Mg concentrations (2.8-13.1 at.%). A ductile-to-brittle transition was observed at 77 K as the Mg content increased from 7.5 to 13.1 at.%, accompanied by a significant decrease in impact energy from 161 J to 14 J. Through detailed theoretical calculations and experimental observations, this composition-dependent transition was found to be primarily associated with Mg segregation-induced grain boundary (GB) expansion and charge density depletion at the GB. These findings not only address the growing demand for durable lightweight materials for low-temperature applications, but also provide insights into the design of ultralight aerospace structural materials capable of withstanding the harsh environments encountered in space exploration.

論文

Coupled dimerized alternating-bond quantum spin chains in the distorted honeycomb-lattice magnet Cu$$_{5}$$SbO$$_{6}$$

Piyakulworawat, C.*; 森田 克洋*; 福元 好志*; Hsieh, W.-Y.*; Chen, W.-T.*; 中島 健次; 河村 聖子; Zhao, Y.*; Wannapaiboon, S.*; Piyawongwatthana, P.; et al.

Physical Review Research (Internet), 8(1), p.013247_1 - 013247_16, 2026/03

https://doi.org/10.1103/vdgg-d128

歪んだハニカム化合物Cu$$_{5}$$SbO$$_{6}$$の中性子非弾性散乱および磁化データを、一次のダイマー展開計算と量子モンテカルロシミュレーションを用いて解析した。これまでに提案されたハニカム格子モデルとは対照的に、この系は相互作用するダイマースピン鎖を有し、鎖に沿って強磁性-反強磁性結合が交互に現れることが示された。さらに、他のCu$$^{2+}$$ベースの歪んだハニカム磁性体で観測される典型的な結合とは異なり、スピン鎖は、予想される層間の鎖間結合ではなく、主にハニカム層間に生じる反強磁性結合を介して結合する。つまり、Cu$$_{5}$$SbO$$_{6}$$の磁気結合スキームが異なることが明らかになった。さらに、X線分光法と透過型電子顕微鏡を利用して、化合物の結晶構造と積層欠陥モデルも従来のモデルをより精密化した。

論文

Magnetic evolution, phase transitions, and electronic band structure of the ferrotoroidic candidate Ba$$_6$$Cr$$_2$$S$$_{10}$$

Zhao, G.*; Li, J.*; Zhang, J.*; 小嶋 健児*; Cai, Y.*; 伊藤 孝; Yoon, S. W.*; Wang, X.*; 前川 禎通*; Su, G.*; et al.

Physical Review Research (Internet), 8(1), p.013331_1 - 013331_10, 2026/03

https://doi.org/10.1103/h576-nnnz

Ferrotoroidic materials, which break both time- and space-reversal symmetries to enhance magnetoelectric responses, are of great interest for applications. Ba$$_6$$Cr$$_2$$S$$_{10}$$, a recently synthesized quasi-one-dimensional ferrotoroidic candidate, combines polarization, magnetization, and toroidal moment, yet its electronic band structure, magnetic evolution, and phase transitions remain incompletely understood to date. Here, we investigate Ba$$_6$$Cr$$_2$$S$$_{10}$$, using electrical transport, direct current magnetization, alternating current susceptibility, specific heat, and muon spin rotation ($$mu$$SR) measurements, along with various first-principles calculations. Electrical transport measurements and density functional theory confirm a narrow band gap ($$sim$$0.707~eV, experimentally; $$sim$$0.680~eV, theoretically). $$mu$$SR measurements reveal that static magnetism dominates down to 2~K, with an ordered volume fraction of $$sim$$89% at this temperature. Two distinct transitions are identified: one around the N$'{e}$el temperature [$$T_{rm N}=(8pm 1)$$~K] and another corresponding to a phase transition near 30~K, as consistently indicated by our complementary experimental techniques. The absence of dynamic critical behaviors and the lack of a $$lambda$$-type specific heat anomaly are consistent with a first-order-like transition at $$T_{rm N}$$. Based on various complementary experimental results and theoretical calculations, we propose a hypothesis that the $$sim$$30~K broad feature arises from the complex interplay between crystal structure distortion and magnetic coupling, which is potentially directly linked to ferrotoroidicity. As the first study integrating $$mu$$SR with complementary experiments and first-principles calculations to explore ferrotoroidicity, this work provides key insights into the underlying physics of Ba$$_6$$Cr$$_2$$S$$_{10}$$ and related compounds in this area.

論文

Unique deformation behavior of ultrafine-grained 304 stainless steel at 20 K

Mao, W.*; Gong, W.; 川崎 卓郎; Gao, S.*; 伊東 達矢; 山下 享介*; Harjo, S.; Zhao, L.*; Wang, Q.*

Scripta Materialia, 264, p.116726_1 - 116726_6, 2025/07

https://doi.org/10.1016/j.scriptamat.2025.116726
 被引用回数：3 パーセンタイル：56.20(Nanoscience & Nanotechnology)

An ultrafine-grained 304 austenitic stainless steel exhibited pronounced serrated Luders deformation at 20 K, with stress and temperature oscillations reaching 200 MPa and 20 K. ${it In-situ}$ neutron diffraction and digital image correlation revealed discontinuous Luders band propagation and burst martensite formation. During deformation, austenite phase stress remained lower than at upper yielding, indicating elastic behavior. Notably, martensite phase stress stayed lower than austenite until fracture, likely due to stress relaxation from burst martensitic transformation at 20 K. The low martensite stress delayed brittle fracture until austenite plastically yielded during uniform deformation.

論文

Magnetism of kagome metals (Fe$$_{1-x}$$Co$$_x$$)Sn studied by $$mu$$SR

Cai, Y.*; Yoon, S.*; Sheng, Q.*; Zhao, G.*; Seewald, E. F.*; Ghosh, S.*; Ingham, J.*; Pasupathy, A. N.*; Queiroz, R.*; Lei, H.*; et al.

Physical Review B, 111(21), p.214412_1 - 214412_17, 2025/06

https://doi.org/10.1103/PhysRevB.111.214412
 被引用回数：2 パーセンタイル：44.75(Materials Science, Multidisciplinary)

We study the magnetic properties of the metallic kagome system (Fe$$_{1-x}$$Co$$_x$$)Sn by a combination of muon spin relaxation ($$mu$$SR), magnetic susceptibility, and scanning tunneling microscopy (STM) measurements in single crystal specimens with Co concentrations $$x$$ = 0, 0.11, 0.8. In the undoped antiferromagnetic compound FeSn, we find possible signatures for a previously unidentified phase that sets in at $$T^{*}sim 50$$~K, well beneath the Neel temperature $$T_{N}sim 376$$~K as indicated by a peak in the relaxation rate 1/$$T_1$$ observed in zero field (ZF) and longitudinal field (LF) $$mu$$SR measurements, with a corresponding anomaly in the ac and dc susceptibility, and an increase in the static width 1/$$T_2$$ in ZF-$$mu$$SR measurements. No signatures of spatial symmetry breaking are found in STM down to 7~K. Related to the location and motion of muons in FeSn, we confirmed a previous report that about 40% of the implanted muons reside at a field-cancelling high symmetry site at $$T < 250$$~K, while an onset of thermal hopping changes the site occupancy at higher temperatures. In Fe$$_{0.89}$$Co$$_{0.11}$$Sn, where disorder eliminated the field-cancellation effect, all the implanted muons exhibit precession and/or relaxation in the ordered state. In Fe$$_{0.2}$$Co$$_{0.8}$$Sn, we find canonical spin glass behavior with freezing temperature $$T_gsim 3.5$$~K; the ZF and LF-$$mu$$SR time spectra exhibit results similar to those observed in dilute alloy spin glasses CuMn and AuFe, with a critical behavior of $$1/T_1$$ at $$T_g$$ and $$1/T_1to 0$$ as $$Tto 0$$. The absence of spin dynamics at low temperatures makes a clear contrast to the spin dynamics observed by $$mu$$SR in many geometrically frustrated spin systems on insulating kagome, pyrochlore, and triangular lattices. The spin glass behavior of CoSn doped with dilute Fe moments is shown to originate primarily from the randomness of doped Fe moments rather than due to geometrical frustration of the underlying lattice.

論文

Brightening triplet excitons enable high-performance white-light emission in organic small molecules via integrating n-$$pi^*/pi$$-$$pi^*$$ transitions

Yang, Q.*; Yang, X.*; Wang, Y.*; Fei, Y.*; Li, F.*; Zheng, H.*; Li, K.*; Han, Y.*; 服部 高典; Zhu, P.*; et al.

Nature Communications (Internet), 15, p.7778_1 - 7778_9, 2024/09

https://doi.org/10.1038/s41467-024-52196-7
 被引用回数：47 パーセンタイル：94.53(Multidisciplinary Sciences)

明るい一重項励起子と三重項励起子を同時に発現する発光材料は、オプトエレクトロニクス、サイネージ、情報暗号化において大きな可能性を秘めている。しかしながら、高性能の白色発光を実現するためには、蛍光と燐光の寄与が不均衡であることが大きな障害となっている。ここでは、水素結合の協同効果による圧力処理エンジニアリングによって、n-$$pi^*/pi$$-$$pi^*$$遷移の混合を実現し、イソフタル酸(IPA)中で三重項状態の発光を7%から40%に高めることで、この課題に対処した。加圧処理したIPAでは、蛍光と燐光のハイブリッドに基づく優れた白色発光が得られ、フォトルミネッセンス量子収率は当初の19%(青色発光)から75%に増加した。その場での高圧IRスペクトル、X線回折、中性子回折から、圧力の上昇に伴い水素結合が連続的に強化されることが明らかになった。さらに、この強化された水素結合は、圧力処理後も常圧条件下まで保持され、バランスの取れた一重項/三重項励起子集団のための効率的な系間交差を目的としたIPAに与え、効率的な白色発光をもたらした。この研究は、有機低分子の三重項状態を明るくするルートを提案するだけでなく、一重項励起子と三重項励起子の比率を調節して、高性能の白色発光を構築するものである。

論文

Probing deformation behavior of a refractory high-entropy alloy using ${it in situ}$ neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

https://doi.org/10.1016/j.jallcom.2023.172635
 被引用回数：8 パーセンタイル：42.29(Chemistry, Physical)

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb)$$_{98}$$$$N_2$$ refractory high-entropy alloy (HEA) during tensile loading has been investigated using ${it in situ}$ neutron diffraction. The equivalent strain-hardening rate of each of the primary $$<hkl>$$-oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses.

論文

Petrophysical properties of representative geological rocks encountered in carbon storage and utilization

Hu, Q.*; Wang, Q. M.*; Zhang, T.*; Zhao, C.*; Iltaf, K. H.*; Liu, S. Q.*; 深津 勇太

Energy Reports (Internet), 9, p.3661 - 3682, 2023/12

https://doi.org/10.1016/j.egyr.2023.02.020
 被引用回数：25 パーセンタイル：73.27(Energy & Fuels)

This study evaluates petrophysical properties of representative geological rocks in the context of injectivity, storage space, and caprock integrity for effective utilization and long-term storage of carbon dioxide. A total of 10 geological rocks were selected as representative storage media for consideration as saline aquifers & depleted oil and gas reservoirs, basalts, and cap rocks, as well as utilization in organic-rich shale and coal seams. An integrated suite of laboratory tests, including liquid immersion porosimetry, gas expansion porosimetry, grain size distribution, mercury intrusion porosimetry, and gas diffusion, were performed on these various rock samples. The results exhibit a disparity of petrophysical properties among two broad groups of rocks: rocks selected for possible storage of CO$$_{2}$$ have porosities of $$sim$$10-25%, permeabilities of $$sim$$10$$^{-16}$$-10$$^{-13}$$ m$$^{2}$$, $$mu$$m-sized pore-throat size distribution, and mostly good pore connectivity; in contrast, the potential caprocks have porosities of $$sim$$0.5-5%, permeabilities of $$sim$$10$$^{-20}$$-10$$^{-18}$$ m$$^{2}$$, pore throat sizes of $$<$$50 nm, and probably poorly connected pore networks. An understanding of the measured facets of pore structure and contribution of fractures is also critical in the context of different testing principles and data interpretation of petrophysical analyses, as well as observational scales in the laboratory and field, and therefore reliable confidence of CO$$_{2}$$ storage and utilization performance. Our work further illustrates the controlling influence of grain size distribution and geological processes on pore size distribution and pore connectivity for a wide range of rock types and lithologies, and particularly presents the extent and behavior of CO$$_{2}$$ gas diffusion with a custom-designed apparatus for a holistic understanding of various petrophysical attributes of widely different geological rocks.

論文

Direct observation of topological magnon polarons in a multiferroic material

Bao, S.*; Gu, Z.-L.*; Shangguan, Y.*; Huang, Z.*; Liao, J.*; Zhao, X.*; Zhang, B.*; Dong, Z.-Y.*; Wang, W.*; 梶本 亮一; et al.

Nature Communications (Internet), 14, p.6093_1 - 6093_9, 2023/09

https://doi.org/10.1038/s41467-023-41791-9
 被引用回数：40 パーセンタイル：95.15(Multidisciplinary Sciences)

Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe$$_{2}$$Mo$$_{3}$$O$$_{8}$$ possessing strong magnon-phonon coupling. Specifically, below the magnetic ordering temperature, a gap opens at the nominal intersection of the original magnon and phonon bands, leading to two separated magnon-polaron bands. Each of the bands undergoes mixing, interconverting and reversing between its magnonic and phononic components. We attribute the formation of magnon polarons to the strong magnon-phonon coupling induced by Dzyaloshinskii-Moriya interaction. Intriguingly, we find that the band-inverted magnon polarons are topologically nontrivial. These results uncover exotic elementary excitations arising from the magnon-phonon coupling, and offer a new route to topological states by considering hybridizations between different types of fundamental excitations.

論文

A Predicted CRISPR-mediated symbiosis between uncultivated archaea

Esser, S. P.*; Rahlff, J.*; Zhao, W.*; Predl, M.*; Plewka, J.*; Sures, K.*; Wimmer, F.*; Lee, J.*; Adam, P. S.*; McGonigle, J.*; et al.

Nature Microbiology (Internet), 8(9), p.1619 - 1633, 2023/09

https://doi.org/10.1038/s41564-023-01439-2
 被引用回数：16 パーセンタイル：78.95(Microbiology)

CRISPR-Cas systems defend prokaryotic cells from viruses, plasmids, and other mobile genetic elements. Capitalizing on multi-omics approaches, we show here that the CRISPR-Cas systems of uncultivated archaea also play an integral role in mitigating potentially detrimental interactions with episymbionts. A comprehensive analysis of CRISPR-Cas-based infection histories revealed that uncultivated deep-subsurface archaeal primary-producers defend themselves from archaeal episymbionts of the DPANN superphylum of archaea, some of which are known to fuse their membranes with their host. We show that host cells counter these attacks by deploying one of two CRISPR-Cas systems (type I-B and type III-A) to target and disrupt essential genes in the episymbiont. However, genome-scale modeling of metabolic interactions between two deep subsurface host-symbiont systems revealed that host cells also benefit from the symbionts via metabolic complementation. We speculate that populations of these uncultivated archaeal episymbionts are currently transitioning from a parasitic lifestyle to one of mutualism, as must have occurred in countless mutualistic systems known today. By expanding our analysis to thousands of archaeal genomes, we conclude that CRISPR-Cas mediated resistance to archaeal episymbiosis evolved independently in various archaeal lineages and may be a wide-spread evolutionary phenomenon.

論文

A One-third magnetization plateau phase as evidence for the Kitaev interaction in a honeycomb-lattice antiferromagnet

Shangguan, Y.*; Bao, S.*; Dong, Z.-Y.*; Xi, N.*; Gao, Y.-P.*; Ma, Z.*; Wang, W.*; Qi, Z.*; Zhang, S.*; Huang, Z.*; et al.

Nature Physics, 19(12), p.1883 - 1889, 2023/09

https://doi.org/10.1038/s41567-023-02212-2
 被引用回数：38 パーセンタイル：94.16(Physics, Multidisciplinary)

The magnetization of a quantum magnet can be pinned at a fraction of its saturated value by collective effects. One example of such a plateau phase is found in spin-1/2 triangular-lattice antiferromagnets. They feature strong geometrical frustration and the plateau phase therein is often interpreted as arising from an order-by-disorder mechanism driven by quantum fluctuations. Here we observe a one-third magnetization plateau under an applied magnetic field in the spin-1 antiferromagnet Na$$_{3}$$Ni$$_{2}$$BiO$$_{6}$$ with a honeycomb lattice, which, with conventional magnetic interactions, would not be geometrically frustrated. Based on our elastic neutron scattering measurements, we propose the spin structure of the plateau phase to be an unusual partial spin-flop ferrimagnetic order. Our theoretical calculations indicate that bond-anisotropic Kitaev interactions are the source of frustration that produces the plateau. These results suggest that Kitaev interactions provide a different route to frustration and phases driven by quantum fluctuations in high-spin magnets.

論文

Two-dimensional quantum universality in the spin-1/2 triangular-lattice quantum antiferromagnet Na$$_{2}$$BaCo(PO$$_{4}$$)$$_{2}$$

Sheng, J.*; Wang, L.*; Candini, A.*; Jiang, W.*; Huang, L.*; Xi, B.*; Zhao, J.*; Ge, H.*; Zhao, N.*; Fu, Y.*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 119(51), p.e2211193119_1 - e2211193119_9, 2022/12

https://doi.org/10.1073/pnas.2211193119
 被引用回数：60 パーセンタイル：96.03(Multidisciplinary Sciences)

Although considerable progress has been made in the theoretical understanding of the low-dimensional frustrated quantum magnets, experimental realizations of a well-established scaling analysis are still scarce. This is particularly true for the two-dimensional antiferromagnetic triangular lattices. Owing to the small exchange strength, the newly discovered compound Na$$_{2}$$BaCo(PO$$_{4}$$)$$_{2}$$ provides a rare opportunity for clarifying the quantum criticality in an ideal triangular lattice with quantum spin S=1/2. In addition to the establishment of the complete phase diagrams, the spin Hamiltonian with a negligible interplane interaction has been determined through the spin wave dispersion in the polarized state, which is consistent with the observation of a two-dimensional quantum critical point with the Bose-Einstein condensation of diluted free bosons.

論文

Two-step Mott transition in Ni(S,Se)$$_2$$; $$mu$$SR studies and charge-spin percolation model

Sheng, Q.*; 金子 竜也*; Yamakawa, Kohtaro*; Guguchia, Z.*; Gong, Z.*; Zhao, G.*; Dai, G.*; Jin, C.*; Guo, S.*; Fu, L.*; et al.

Physical Review Research (Internet), 4(3), p.033172_1 - 033172_14, 2022/09

https://doi.org/10.1103/PhysRevResearch.4.033172

A pyrite system NiS$$_{2-x}$$Se$$_x$$ exhibits a bandwidth controlled Mott transition via (S,Se) substitutions in a two-step process: the antiferromagnetic insulator (AFI) to antiferromagnetic metal (AFM) transition at $$xsim$$0.45 followed by the AFM to paramagnetic metal (PMM) transition at $$xsim$$1.0. Among a few other Mott systems which exhibit similar two-step transitions, Ni(S,Se)$$_2$$ is of particular interest because a large intermediate AFM region in the phase diagram would provide unique opportunities to study the interplay between the spin and charge order. By comparing and combining our muon spin relaxation studies and previous neutron scattering studies, here we propose a picture where the spin order is maintained by the percolation of "nonmetallic" localized and dangling Ni moments surrounded by S, while the charge transition from AFI to AFM is caused by the percolation of the conducting paths generated by the Ni-Se-Ni bonds.

論文

Environmental effects on layer-dependent dynamics of Dirac fermions in quasicrystalline bilayer graphene

Zhao, Y.*; Suzuki, T.*; Iimori, T.*; Kim, H.-W.*; Ahn, J. R.*; 堀尾 眞史*; 佐藤 祐輔*; 深谷 有喜; Kanai, T.*; Okazaki, K.*; et al.

Physical Review B, 105(11), p.115304_1 - 115304_8, 2022/03

https://doi.org/10.1103/PhysRevB.105.115304
 被引用回数：3 パーセンタイル：16.20(Materials Science, Multidisciplinary)

本研究では、時間・角度分解光電子分光を用いて、SiC基板上に作製したグラフェン層におけるキャリアダイナミクスについて調べた。光ポンピング後の準結晶グラフェンのディラックバンドでは、電子ドーピングに層依存性が観測された。また、光誘起キャリア輸送量は基板からの距離に依存することがわかった。フラット基板及びステップ基板上の単層グラフェンの結果から、キャリアの生成源は界面のステップ状態に由来することがわかった。本メカニズムは、密度汎関数計算による電子構造を基にした動的モデルにより記述できる。

論文

Evidence for strong correlations at finite temperatures in the dimerized magnet Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$

Shangguan, Y.*; Bao, S.*; Dong, Z.-Y.*; Cai, Z.*; Wang, W.*; Huang, Z.*; Ma, Z.*; Liao, J.*; Zhao, X.*; 梶本 亮一; et al.

Physical Review B, 104(22), p.224430_1 - 224430_8, 2021/12

https://doi.org/10.1103/PhysRevB.104.224430
 被引用回数：4 パーセンタイル：17.76(Materials Science, Multidisciplinary)

Dimerized magnets forming alternating Heisenberg chains exhibit quantum coherence and entanglement and thus can find potential applications in quantum information and computation. However, magnetic systems typically undergo thermal decoherence at finite temperatures. Here, we show inelastic neutron scattering results on an alternating antiferromagnetic-ferromagnetic chain compound Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$ that the excited quasiparticles can counter thermal decoherence and maintain strong correlations at elevated temperatures. At low temperatures, we observe clear dispersive singlet-triplet excitations arising from the dimers formed along the crystalline $$b$$-axis. The excitation gap is of $$sim$$18 meV and the bandwidth is about half of the gap. The band top energy has a weak modulation along the [100] direction, indicative of a small interchain coupling. The gap increases while the bandwidth decreases with increasing temperature, leading to a strong reduction in the available phase space for the triplons. As a result, the Lorentzian-type energy broadening becomes highly asymmetric as the temperature is raised. These results are associated with a strongly correlated state resulting from hard-core constraint and quasiparticle interactions. We consider these results to be not only evidence for strong correlations at finite temperatures in Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$, but also for the universality of the strongly correlated state in a broad range of quantum magnetic systems.

論文

Certification of uranium isotope amount ratios in a suite of uranium ore concentrate certified reference materials

Zhang, R.*; Nadeau, K.*; Gautier, E. A.*; Babay, P. A.*; Ramella, J. L.*; Virgolici, M.*; Serban, A. E.*; Fugaru, V.*; 木村 祥紀; Venchiarutti, C.*; et al.

Geostandards and Geoanalytical Research, 46(1), p.43 - 56, 2021/11

https://doi.org/10.1111/ggr.12409
 被引用回数：10 パーセンタイル：47.97(Geochemistry & Geophysics)

In this study, data from thirteen laboratories from around the world are presented for a successful certification of uranium isotope ratios in uranium ore concentrate certified reference materials from the National Research Council Canada. Different mass spectrometric techniques (including SF-ICPMS, q-ICM-MS, TIMS, MC-ICP-MS, SIMS, and AMS) and analytical methods were employed. In general, the reported data from all sources exhibit good consistency, and as expected TIMS and MC-ICP-MS showed superior performances. The three candidate uranium ore concentrate CRMs, UCLO-1, UCHI-1, and UPER-1, have natural uranium isotope ratios with certified values of 0.5304(7)$$times$$10$$^{-4}$$, 0.5475(2)$$times$$10$$^{-4}$$, and 0.5361(4)$$times$$10$$^{-4}$$ for n($$^{234}$$U)/n($$^{238}$$U) and 0.007 2563(13), 0.007 2563(10), and 0.007 2542(11) for n($$^{235}$$U)/n($$^{238}$$U), respectively, with expanded uncertainty (k=2) applicable to the last digit of the value given in the parentheses. Information values for n($$^{236}$$U)/n($$^{238}$$U) in these three CRMs, measured by AMS, are also provided: 10$$times$$10$$^{-12}$$, 2$$times$$10$$^{-12}$$, and 22$$times$$10$$^{-12}$$. The uncertainties of the proposed certified values of uranium isotope ratios in uranium ore concentrate CRMs are superior to available reference materials and the values of n($$^{234}$$U)/n($$^{238}$$U) and n($$^{236}$$U)/n($$^{238}$$U) show significant variation among the three CRMs.

論文

Field-tuned magnetic structure and phase diagram of the honeycomb magnet YbCl$$_3$$

Hao, Y. Q.*; Wo, H. L.*; Gu, Y. M.*; Zhang, X. W.*; Gu, Y. Q.*; Zheng, S. Y.*; Zhao, Y.*; Xu, G. Y.*; Lynn, J. W.*; 中島 健次; et al.

Science China; Physics, Mechanics & Astronomy, 64(3), p.237411_1 - 237411_6, 2021/03

https://doi.org/10.1007/s11433-020-1626-3
 被引用回数：13 パーセンタイル：65.00(Physics, Multidisciplinary)

We report thermodynamic and neutron diffraction measurements on the magnetic ordering properties of the honeycomb lattice magnet YbCl$$_3$$. We find YbCl$$_3$$ exhibits a N${'e}$el type long-range magnetic order at the wavevector (0, 0, 0) below T$$_N$$ = 600 mK. This magnetic order is associated with a small sharp peak in heat capacity and most magnetic entropy release occurs above the magnetic ordering temperature. The magnetic moment lies in-plane, parallel to the monoclinic a-axis, whose magnitude m$$_{rm Yb}$$ = 0.86(3) $$mu_B$$ is considerably smaller than the expected fully ordered moment of 2.24 $$mu_B$$ for the doublet crystal-field ground state. The magnetic ordering moment gradually increases with increasing magnetic field perpendicular to the ab-plane, reaching a maximum value of 1.6(2) $$mu_B$$ at 4 T, before it is completely suppressed above $$sim$$9 T. These results indicate the presence of strong quantum fluctuations in YbCl$$_3$$.

論文

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

https://doi.org/10.1021/acs.nanolett.0c04244
 被引用回数：116 パーセンタイル：97.48(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.

論文

Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

https://doi.org/10.1103/PhysRevLett.122.217003
 被引用回数：9 パーセンタイル：50.21(Physics, Multidisciplinary)

We report neutron scattering measurements of single-crystalline YFe$$_{2}$$Ge$$_{2}$$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe$$_{2}$$Ge$$_{2}$$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe$$_{2}$$Ge$$_{2}$$ displays anisotropic stripe-type antiferromagnetic spin fluctuations at ($$pi, 0, pi$$). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector ($$0, 0, pi$$). These ferromagnetic spin fluctuations are isotropic in the ($$H, K$$) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe$$_{2}$$Ge$$_{2}$$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.

論文

Nature of dynamic ferrite transformation revealed by ${it in-situ}$ neutron diffraction analysis during thermomechanical processing

柴田 曉伸*; 竹田 泰成*; Park, N.*; Zhao, L.*; Harjo, S.; 川崎 卓郎; Gong, W.*; 辻 伸泰*

Scripta Materialia, 165, p.44 - 49, 2019/05

https://doi.org/10.1016/j.scriptamat.2019.02.017
 被引用回数：43 パーセンタイル：84.62(Nanoscience & Nanotechnology)

Nowadays, a new concept of process utilizing dynamic ferrite transformation, which can achieve ultrafine-grained structure with a mean grain size of approximately 1$$mu$$m, has been proposed. This paper reports transformation mode of dynamic ferrite transformation and formation mechanism of ultrafine-grained structure revealed by our novel technique of ${it in-situ}$ neutron diffraction analysis during thermomechanical processing. Dynamic ferrite transformation occurs in a diffusional manner, whose partitioning behavior changes from para- to ortho-equilibrium with the progress of transformation. Moreover, we propose that dynamic recrystallization of dynamically-transformed ferrite is the main mechanism for the formation of ultrafine-grained structure.

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