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論文

Oxygen interstitials make metastable $$beta$$ titanium alloys strong and ductile

Chong, Y.*; Gholizadeh, R.*; Guo, B.*; 都留 智仁; Zhao, G.*; 吉田 周平*; 光原 昌寿*; Godfrey, A.*; 辻 伸泰*

Acta Materialia, 257, p.119165_1 - 119165_14, 2023/09

https://doi.org/10.1016/j.actamat.2023.119165
 被引用回数：5 パーセンタイル：87.83(Materials Science, Multidisciplinary)

$$beta$$チタン合金は、優れた歪み硬化能を有する反面、降伏強度が低いという問題を抱えている。ここでは、Ti-12Mo(wt.%)準安定$$beta$$チタン合金の降伏強度の向上における結晶粒の微細化と格子間物質の添加の寄与について検討した。その結果、結晶粒の微細化は材料を強化するどころか、この合金の極限引張強度を低下させることがわかった。この予想外の異常な挙動は、ひずみ誘起$$alpha^{primeprime}$$マルテンサイト相変態が著しく促進されたことに起因しており、その場観察放射光X線回折分析により、この相が$$beta$$相よりはるかに軟らかいことが初めて明らかになった。また、酸素添加と結晶粒微細化の組み合わせにより、Ti-12Mo-0.3O(wt.%)合金において前例のない強度と延性の相乗効果が得られることが判明した。この三元合金における酸素溶質には2つの有利な点がある。第一に、溶質酸素は、微細な組織においても、歪みによる$$alpha^{primeprime}$$マルテンサイト相への変態を大きく抑制し、過剰な$$alpha^{primeprime}$$マルテンサイトによる軟化効果を回避することができる。次に、アトムプローブトモグラフィーで明らかになったように、酸素溶質が双晶境界に偏析しやすい。これにより、$${332}langle113rangle$$変形双晶の成長が抑制され、より広範な双晶の核生成が促進される。本研究で得られた知見は、強靭な準安定$$beta$$チタン合金を設計するための費用対効果の高い根拠となり、この高強度対重量構造材料のさらなる普及に大きな意味を持つ。

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：4 パーセンタイル：56.47(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

Magnetic properties and electronic configurations of Mn ions in the diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ studied by X-ray magnetic circular dichroism and resonant inelastic X-ray scattering

鈴木 博人*; Zhao, G.*; 岡本 淳*; 坂本 祥哉*; Chen, Z.-Y.*; 野中 洋亮*; 芝田 悟朗; Zhao, K.*; Chen, B.*; Wu, W.-B.*; et al.

Journal of the Physical Society of Japan, 91(6), p.064710_1 - 064710_5, 2022/06

https://doi.org/10.7566/JPSJ.91.064710
 被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

The magnetic properties and the electronic excitations of the new diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ have been studied by X-ray magnetic circular dichroism (XMCD) and resonant inelastic X-ray scattering (RIXS). The sum rule analysis of the XMCD spectra indicates that the Mn atoms are in the high-spin configurations of $$d^5$$, whereas the presence of competing ferromagnetic and antiferromagnetic interactions between the Mn ions reduces the net spin moment. Based on a comparison of the RIXS line shapes with those of Ga$$_{1-x}$$Mn$$_x$$As, it is concluded that the ground state of Mn in Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ consists of both the $$3d^5 underline{L}$$ and $$3d^5$$ electron configurations.

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：6 パーセンタイル：60.19(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

Coordination number regulation of molybdenum single-atom nanozyme peroxidase-like specificity

Wang, Y.*; Jia, G.*; Cui, X.*; Zhao, X.*; Zhang, Q.*; Gu, L.*; Zheng, L.*; Li, L. H.*; Wu, Q.*; Singh, D. J.*; et al.

Chem, 7(2), p.436 - 449, 2021/02

https://doi.org/10.1016/j.chempr.2020.10.023
 被引用回数：199 パーセンタイル：99.81(Chemistry, Multidisciplinary)

Nanozymes are promising alternatives to natural enzymes, but their use remains limited owing to poor specificity. Overcoming this is extremely challenging due to the intrinsic structural complexity of these systems. We report theoretical design and experimental realization of a series of heterogeneous molybdenum single-atom nanozymes (named Mo$$_{rm{SA}}$$-N$$_{x}$$-C), wherein we find that the peroxidase-like specificity is well regulated by the coordination numbers of single Mo sites. The resulting Mo$$_{rm{SA}}$$-N$$_{3}$$-C catalyst shows exclusive peroxidase-like behavior. It achieves this behavior via a homolytic pathway, whereas Mo$$_{rm{SA}}$$-N$$_{2}$$-C and Mo$$_{rm{SA}}$$-N$$_{4}$$-C catalysts have a different heterolytic pathway. The mechanism of this coordination-number-dependent enzymatic specificity is attributed to geometrical structure differences and orientation relationships of the frontier molecular orbitals.

論文

Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe$$_{2-x}$$T$$_{x}$$As$$_{2}$$ ($$T$$ = Co,Ni)

Tam, D. M.*; Song, Y.*; Man, H.*; Cheung, S. C.*; Yin, Z.*; Lu, X.*; Wang, W.*; Frandsen, B. A.*; Liu, L.*; Gong, Z.*; et al.

Physical Review B, 95(6), p.060505_1 - 060505_6, 2017/02

https://doi.org/10.1103/PhysRevB.95.060505
 被引用回数：23 パーセンタイル：71.14(Materials Science, Multidisciplinary)

We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on the antiferromagnetic (AF) orthorhombic phase in BaFe$$_{2-x}$$T$$_{x}$$As$$_{2}$$ and its Co- and Ni-substituted members near optimal superconductivity. In the low-temperature AF ordered state, uniaxial pressure necessary to detwin the orthorhombic crystals also increases the magnetic ordered moment, reaching an 11% increase under 40 MPa for BaFe$$_{1.9}$$Co$$_{0.1}$$As$$_2$$, and a 15% increase for BaFe$$_{1.915}$$Ni$$_{0.085}$$As$$_2$$. We also observe an increase of the AF ordering temperature ($$T_N$$) of about 0.25 K/MPa in all compounds, consistent with density functional theory calculations that reveal better Fermi surface nesting for itinerant electrons under uniaxial pressure. The doping dependence of the magnetic ordered moment is captured by combining dynamical mean field theory with density functional theory, suggesting that the pressure-induced moment increase near optimal superconductivity is closely related to quantum fluctuations and the nearby electronic nematic phase.

論文

Spin excitations in optimally P-doped BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$ superconductor

Hu, D.*; Yin, Z.*; Zhang, W.*; Ewings, R. A.*; 池内 和彦*; 中村 充孝; Roessli, B.*; Wei, Y.*; Zhao, L.*; Chen, G.*; et al.

Physical Review B, 94(9), p.094504_1 - 094504_7, 2016/09

AA2016-0252.pdf:2.18MB

https://doi.org/10.1103/PhysRevB.94.094504
 被引用回数：16 パーセンタイル：59.05(Materials Science, Multidisciplinary)

最適Pドープされた超伝導体BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$ (T$$_c$$=30K)におけるスピン励起の温度及びエネルギー依存性が非弾性中性子散乱実験を使って調べられた。我々の実験結果は密度汎関数理論や動的平均場理論で予想される計算結果と矛盾しておらず、BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$における平均プニクトゲン高さの減少が、電子相関の強さを弱め、磁気励起の有効バンド幅の増加に寄与することを示唆している。

論文

Phase behavior and Li$$^{+}$$ ion conductivity of styrene-ethylene oxide multiblock copolymer electrolytes

Sarapas, J. M.*; 西条 賢次*; Zhao, Y.; 竹中 幹人*; Tew, G. N.*

Polymers for Advanced Technologies, 27(7), p.946 - 954, 2016/07

https://doi.org/10.1002/pat.3753
 被引用回数：10 パーセンタイル：35.79(Polymer Science)

A molecular weight series of PS-PEO multiblock copolymers was synthesized by the thiol-norbornene click reaction. These materials were characterized both as neat and lithium $$bis$$-trifluorosulfonimide salt loading samples. The neat samples demonstrated the crystallinity increases with PEO contents. The lithium ion-containing samples had broad scattering peaks, half of which displayed disordered scattering. Fitting of disordered scattering peaks by the random phase approximation, yielded the effective Flory-huggins parameter ($$chi$$$$_{RPA}$$) and radius of gyration ($$R$$$$_{g}$$) values that were compared to recent predictive works by Balsara and coworkers. The samples were also analyzed by electrochemical impedance spectroscopy for their potential to conduct lithium ions and those with the volume fraction of PEO larger than 0.5 demonstrated robust conductivity.

論文

Spatio-temporal evolution of the L$$rightarrow$$H and H$$rightarrow$$L transitions

三木 一弘; Diamond, P. H.*; Fedorczak, N.*; G$"u$rcan, $"O$. D.*; Malkov, M.*; Lee, C.*; 小菅 祐輔*; Tynan, G. R.*; Xu, G. S.*; Estrada, T.*; et al.

Nuclear Fusion, 53(7), p.073044_1 - 073044_10, 2013/07

https://doi.org/10.1088/0029-5515/53/7/073044
 被引用回数：25 パーセンタイル：72.11(Physics, Fluids & Plasmas)

L$$rightarrow$$H, H$$rightarrow$$L遷移の理解はITER運用の成否に重要である。この論文で我々は新たな理論モデル研究を紹介して、遷移の時空間ダイナミクスを調べる。ここで帯状流の役割、そしてダイナミクスと輸送しきい値の間にあるマクロとミクロの接続について強調する。モデルは5場で、簡略化された座標系で、時間と1次元の空間発展を解く。この論文の内容は次の通りである。(a)モデルの基礎方程式とL$$rightarrow$$I$$rightarrow$$H遷移の時空間発展、(b)$$nabla$$Bドリフトの非対称性で輸送しきい値が変化することの物理的な説明、(c)熱雪崩現象がL$$rightarrow$$I$$rightarrow$$H遷移のしきい値変位に与える影響、(d)H$$rightarrow$$L逆遷移のダイナミクスとヒステリシスの物理。

論文

Signature splitting inversion and backbending in $$^{80}$$Rb

He, C.*; Shen, S.*; Wen, S.*; Zhu, L.*; Wu, X.*; Li, G.*; Zhao, Y.*; Yan, Y.*; Bai, Z.*; Wu, Y.*; et al.

Physical Review C, 87(3), p.034320_1 - 034320_10, 2013/03

https://doi.org/10.1103/PhysRevC.87.034320
 被引用回数：6 パーセンタイル：43.56(Physics, Nuclear)

High-spin states of $$^{80}$$Rb are studied via the fusion-evaporation reactions $$^{65}$$Cu+$$^{19}$$F, $$^{66}$$Zn+$$^{18}$$O, and $$^{68}$$Zn+$$^{16}$$O with the beam energies of 75 MeV, 76 MeV, and 80 MeV, respectively. Twenty-three states with twenty-eight $$gamma$$ transitions are added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22$$^-$$ and 15$$^-$$ and two sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the $$alpha$$ = 0 branch as well as another one in the $$alpha$$ =1 branch of the second negative-parity band are observed. Signature inversions occur in the positive-parity and first negative-parity bands at the spins of 11$$hbar$$ and 16$$hbar$$, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone $$^{82}$$Y. Signature inversion in the positive-parity yrast band with configuration $$pi$$g9/2 $$otimes$$ $$nu$$g9/2 in this nucleus is discussed using the projected shell model.

論文

Plasma boundary and first-wall diagnostics in ITER

Pitcher, C. S.*; Andrew, P.*; Barnsley, R.*; Bertalot, L.*; Counsell, G. G.*; Encheva, A.*; Feder, R. E.*; 波多江 仰紀; Johnson, D. W.*; Kim, J.*; et al.

Journal of Nuclear Materials, 415(Suppl.1), p.S1127 - S1132, 2011/08

https://doi.org/10.1016/j.jnucmat.2011.01.111
 被引用回数：0 パーセンタイル：0.01(Materials Science, Multidisciplinary)

ITER plasma boundary and first-wall diagnostics are summarized in terms of their physical implementation and physics motivation. The challenge of extracting diagnostic signals while maintaining nuclear shielding is discussed, as well as the problems associated with high levels of erosion and redeposition.

論文

Experimental constraints on the phase diagram of titanium metal

Zhang, J.*; Zhao, Y.*; Hixson, R. S.*; Gray III, G. T.*; Wang, L.*; 内海 渉; 齋藤 寛之; 服部 高典

Journal of Physics and Chemistry of Solids, 69(10), p.2559 - 2563, 2008/10

https://doi.org/10.1016/j.jpcs.2008.05.016
 被引用回数：29 パーセンタイル：72.69(Chemistry, Multidisciplinary)

The phase transformations of titanium metal have been studied at temperatures and pressures up to 973 K and 8.7 GPa using synchrotron X-ray diffraction. An update, more accurate phase diagram is established for Ti metal based on the present observations and previous constraints on the $$alpha$$-$$beta$$ and $$omega$$-$$beta$$ phase boundaries.

論文

Thermal equations of state for titanium obtained by high pressure-temperature diffraction studies

Zhang, J.*; Zhao, Y.*; Hixson, R. S.*; Gray III, G. T.*; Wang, L.*; 内海 渉; 齋藤 寛之; 服部 高典

Physical Review B, 78(5), p.054119_1 - 054119_7, 2008/08

https://doi.org/10.1103/PhysRevB.78.054119
 被引用回数：54 パーセンタイル：85.29(Materials Science, Multidisciplinary)

We have conducted in situ high-pressure diffraction experiments on titanium metal at pressures up to 8.2 GPa and temperatures up to 900 K. From the pressure-volume-temperature measurements, thermoelastic parameters were derived for titanium based on a modified high-T Birch-Murnaghan equation of state and a thermal pressure approach.

論文

Magnetic resonance studies of defects in electron-irradiated ZnO substrates

Son, N. T.*; Ivanov, I. G.*; Kuznetsov, A. Yu.*; Svensson, B. G.*; Zhao, Q. X.*; Willander, M.*; 森下 憲雄; 大島 武; 伊藤 久義; 磯谷 順一*; et al.

Physica B; Condensed Matter, 401-402, p.507 - 510, 2007/12

https://doi.org/10.1016/j.physb.2007.09.010
 被引用回数：3 パーセンタイル：17.83(Physics, Condensed Matter)

酸化亜鉛(ZnO)中の欠陥の挙動を解明するために、3又は6MeV電子線照射を行ったZnOの光検知磁気共鳴(ODMR)評価を行った。その結果、浅いドナー及びZu空孔に起因するシグナルに加え、スピン1/2を有する幾つかのシグナルが観測され、このうち、LU3及びLU4とラベル付けされたシグナルがキャリアの再結合中心として働くことが判明した。また、400$$^{circ}$$Cまでの熱処理後もLU3,LU4は安定に存在することも併せて明らかとなった。

論文

Recombination centers in as-grown and electron-irradiated ZnO substrates

Son, N. T.*; Ivanov, G.*; Kuznetsov, A.*; Svensson, B. G.*; Zhao, Q. X.*; Willander, M.*; 森下 憲雄; 大島 武; 伊藤 久義; 磯谷 順一*; et al.

Journal of Applied Physics, 102(9), p.093504_1 - 093504_5, 2007/11

https://doi.org/10.1063/1.2802186
 被引用回数：18 パーセンタイル：56.64(Physics, Applied)

室温にて3MeV電子線照射したZnO中に発生する欠陥をODMR(Optical detection of magnetic resonance)を用いて調べた。その結果、キャリアの再結合中心として働くZn空孔に起因する欠陥及びその他幾つかの空孔型欠陥が観測された(LU1$$sim$$LU6センター)。また、電子線未照射のZnOに関しても併せてODMR測定を行ったところ、電子線照射ZnOで観測された欠陥のうち、Zn空孔及びその他の空孔に起因する欠陥であるLU3及びLU4センターが観測された。このことから、LU3及びLU4センターはキャリア再結合中心として働く真性欠陥であることが結論できた。

論文

Experimental progress on zonal flow physics in toroidal plasmas

藤澤 彰英*; 井戸 毅*; 清水 昭博*; 岡村 昇一*; 松岡 啓介*; 井口 春和*; 浜田 泰司*; 中野 治久*; 大島 慎介*; 伊藤 公孝*; et al.

Nuclear Fusion, 47(10), p.S718 - S726, 2007/10

https://doi.org/10.1088/0029-5515/47/10/S19
 被引用回数：101 パーセンタイル：95.24(Physics, Fluids & Plasmas)

帯状流の物理の実験的進展につきレビューする。新しい測定器により、プラズマ中の帯状流の存在が確認され、その時間空間特性,乱流や閉じ込めとの関係が明らかにされてきた。特に、測地的音波モードという振動帯状流について、測定結果が集積し、理論的進展をうながしている。乱流による帯状流の生成機構も解明されつつある。各国の装置の結果を比較,協力することにより、今後もなお一層、帯状流と閉じ込めとの関係の解明を進めることが重要である。

論文

Experimental progress on zonal flow physics in toroidal plasmas

藤澤 彰英*; 井戸 毅*; 清水 昭博*; 岡村 昇一*; 松岡 啓介*; 浜田 泰司*; 星野 克道; 永島 芳彦*; 篠原 孝司; 中野 治久*; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 12 Pages, 2007/03

http://www-naweb.iaea.org/napc/physics/FEC/FEC2006/html/node104.htm#26311

帯状流に関する実験の現状についてまとめる。測定の進歩により、帯状流の存在,時間空間特性,乱流との関係,閉じ込めとの関係などが明らかになりつつある。特に、帯状流の一種である測地的音波モードの測定結果の集積により、これを記述できる理論の構築が必要となっている。これらの帯状流と閉じ込めの解明をさらに進めるためには、装置間の横断的研究が非常に有効であると考えられる。

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