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Anomalous small-angle X-ray scattering (ASAXS) study of irradiation-induced nanostructure change in Fe-ion beam irradiated oxide dispersion-strengthened (ODS) steel

熊田 高之; 大場 洋次郎; 元川 竜平; 諸岡 聡; 冨永 亜希; 谷田 肇; 菖蒲 敬久; 金野 杏彩; 大和田 謙二*; 大野 直子*; et al.

Journal of Nuclear Materials, 528, p.151890_1 - 151890_7, 2020/01

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)



Effect of $$B$$-site randomness on the antiferroelectric/relaxor nature of the ground state; Diffuse and inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$

大和田 謙二*; 塚田 慎也*; 福田 竜生; 筒井 智嗣*; Baron, A. Q. R.*; 水木 純一郎*; 大和 英弘*; 安田 直彦*; 寺内 暉*

Physical Review B, 98(5), p.054106_1 - 054106_10, 2018/08

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

The effect of $$B$$-site randomness on the antiferroelectric/relaxor nature of the ground state was investigated by studying diffuse and inelastic X-ray scattering from ordered and disordered Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$ (O- and D-PIN) single crystals. The diffuse scattering measurement of O-PIN (antiferroelectric at $$T<T_N$$) shows the existence of ferroelectrically interactive local polarization above $$T_N$$. Inelastic X-ray scattering shows that the transverse-acoustic (TA) and transverse-optic (TO) modes are dominant at $$Tsim$$800 K, while the central peak (CP) and TA modes are coupled and majorly contribute to the critical behavior of the diffuse scattering at $$T_N$$. Upon these results, the $$B$$-site randomness is discussed in terms of suppressing the antiferroelectric instability and enhancing the polarization fluctuation.


Chemical form analysis of reaction products in Cs-adsorption on stainless steel by means of HAXPES and SEM/EDX

小畠 雅明; 岡根 哲夫; 中島 邦久; 鈴木 恵理子; 大和田 謙二; 小林 啓介*; 山上 浩志; 逢坂 正彦

Journal of Nuclear Materials, 498, p.387 - 394, 2018/01

 被引用回数:7 パーセンタイル:13.66(Materials Science, Multidisciplinary)



Mineralogical characterization of radioactive particles from Fukushima soil using $$mu$$-XRD with synchrotron radiation

甕 聡子*; 向井 広樹*; 綿貫 徹; 大和田 謙二; 福田 竜生; 町田 晃彦; 倉又 千咲*; 菊池 亮佑*; 矢板 毅; 小暮 敏博*

Journal of Mineralogical and Petrological Sciences, 111(5), p.305 - 312, 2016/10

 被引用回数:11 パーセンタイル:36.63(Mineralogy)



Negative correlation between electrical response and domain size in a Ti-composition-gradient Pb[(Mg$$_{1/3}$$Nb$$_{2/3}$$)$$_{1-x}$$Ti$$_{x}$$]O$$_{3}$$ crystal near the morphotropic phase boundary

清水 大輔*; 塚田 慎也*; 松浦 直人*; 坂本 潤哉*; 小島 誠治*; 並河 一道*; 水木 純一郎; 大和田 謙二

Physical Review B, 92(17), p.174121_1 - 174121_5, 2015/11

 被引用回数:7 パーセンタイル:57.17(Materials Science, Multidisciplinary)



Spontaneous formation of suboxidic coordination around Co in ferromagnetic rutile Ti$$_{0.95}$$Co$$_{0.05}$$O$$_2$$ film

Hu, W.*; 林 好一*; 福村 知昭*; 赤木 和人*; 塚田 捷*; 八方 直久*; 細川 伸也*; 大和田 謙二; 高橋 正光; 鈴木 基寛*; et al.

Applied Physics Letters, 106(22), p.222403_1 - 222403_5, 2015/06

 被引用回数:28 パーセンタイル:17.47(Physics, Applied)

The local atomic structures around Co in high temperature diluted ferromagnetic semiconductor Co-doped TiO$$_2$$ has been investigated using X-ray fluorescence holography and X-ray absorption fine structure experiments. While the Co atoms in the Ti$$_{0.99}$$Co$$_{0.01}$$O$$_2$$ simply substituted for Ti sites in the rutile structure, a suboxidic arrangement of CoO$$_2$$Ti$$_4$$ was found to form around Co in the Ti$$_{0.95}$$Co$$_{0.05}$$O$$_2$$ films. First-principles calculations supported the stability of the aggregated suboxidic clusters in the rutile TiO$$_2$$. The suboxidic coordination may be the source of strong exchange interaction, resulting in the high Curie temperature in Co-dopedTiO$$_2$$.


Heterophase fluctuations near $$T_{rm c}$$ in the relaxor ferroelectrics (1-x)Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-xPbTiO$$_{3}$$ ($$x$$ = 0.09) studied by X-ray diffuse scattering and coherent X-ray scattering

大和田 謙二; 水木 純一郎*; 松下 三芳*; 並河 一道*

Physical Review B, 90(10), p.104109_1 - 104109_12, 2014/09

 被引用回数:5 パーセンタイル:68.96(Materials Science, Multidisciplinary)



Acute and obtuse rhombohedrons in the local structures of relaxor ferroelectric Pb(Mg$$_{1/3}$$Nb$$_{2/3}$$)O$$_3$$

Hu, W.*; 林 好一*; 大和田 謙二; Chen, J.*; 八方 直久*; 細川 伸也*; 高橋 正光; Bokov, A.*; Ye, Z.-G*

Physical Review B, 89(14), p.140103_1 - 140103_5, 2014/04

 被引用回数:33 パーセンタイル:15.31(Materials Science, Multidisciplinary)

The local structures around Nb and Pb in the relaxor ferroelectric Pb(Mg$$_{1/3}$$Nb$$_{2/3}$$)O$$_3$$ were investigated by X-ray fluorescence holography. The Pb atomic images around Nb showed a rhombohedral distortion of the crystal unit cells. The Pb-Pb correlated images showed a local structure of body-center-like $$2a_0times 2a_0 times 2a_0$$ superlattice, proving a rigid three-dimensional network structural model combining the two kinds of rhombohedrons. This superstructure and the fluctuating Pb and Nb atoms play an important role in the relaxor behavior of this material.



大和田 謙二

高圧力の科学と技術, 23(3), p.245 - 251, 2013/08



Damped soft phonons and diffuse scattering in (Bi$$_{1/2}$$Na$$_{1/2}$$)TiO$$_{3}$$

松浦 直人*; 飯田 裕之*; 廣田 和馬*; 大和田 謙二; 野口 祐二*; 宮山 勝*

Physical Review B, 87(6), p.064109_1 - 064109_10, 2013/02

 被引用回数:23 パーセンタイル:23.86(Materials Science, Multidisciplinary)



リラクサーにおけるランダムネスとフラストレーション; Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$の構造物性研究

大和田 謙二

日本結晶学会誌, 54(3), p.147 - 154, 2012/06



Two-dimensional charge fluctuation in $$beta$$-Na$$_{0.33}$$V$$_{2}$$O$$_{5}$$

大和田 謙二; 山内 徹*; 藤井 保彦*; 上田 寛*

Physical Review B, 85(13), p.134102_1 - 134102_4, 2012/04

 被引用回数:7 パーセンタイル:62.81(Materials Science, Multidisciplinary)



X-ray photon correlation spectroscopy of structural fluctuations in relaxor ferroelectrics PZN-9%PT

大和田 謙二; 下村 晋*; 中尾 裕則*; 松下 三芳*; 並河 一道*; 水木 純一郎

Journal of Physics; Conference Series, 320, p.012086_1 - 012086_5, 2011/09

 被引用回数:0 パーセンタイル:100

91$$%$$Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9$$%$$PbTiO$$_{3}$$においてX線光子相関分光を行い、$$T_{rm C}$$近傍において遅い構造揺らぎを見いだした。その遅い構造揺らぎは遅い成分と早い成分からなる。われわれは早い成分を抽出し10秒ほどの緩和時間を得た。これらの揺らぎはマクロな正方晶とミクロな射法対称性の競合によるものであり、低周波誘電率を与えるものであると推測される。


Effect of B-site randomness on the antiferroelectric/relaxor nature of the ground state; Inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

大和田 謙二; 福田 竜生; 水木 純一郎; 廣田 和馬*; 寺内 暉*; 筒井 智嗣*; Baron, A. Q. R.*; 大和 英弘*; 安田 直彦*

Journal of the Korean Physical Society, 59(3), p.2509 - 2514, 2011/09

 被引用回数:2 パーセンタイル:77.51(Physics, Multidisciplinary)

Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$(PIN)はペロヴスカイトBサイトの秩序度により反強誘電状態,強誘電状態,リラクサー状態を取りうる物質である。秩序PINは鉛複合ペロヴスカイトPb(B'B'')O$$_{3}$$においてBサイトランダムネスのない系であり、Bサイトランダムネスによる反強誘電状態/リラクサー状態の起源を探るには理想的な物質である。われわれはX線非弾性散乱実験を行った。準弾性散乱(QE)は臨界スローダウンを示し横波音響(TA)フォノンは反強誘電転移点($$T_{rm N}$$)までソフト化を示す一方、横波光学モードは低温までソフト化を続けた。これらの結果は、反強誘電相転移はQEの起源とTAフォノンによるものであるが、強誘電相関は確固としてその背後に存在していることを示している。これらの結果を元に、Bサイトランダムネスの効果について議論する。


Polarization-analyzed resonant inelastic X-ray scattering of the orbital excitations in KCuF$$_3$$

石井 賢司; 石原 純夫*; 村上 洋一*; 池内 和彦*; 葛下 かおり*; 稲見 俊哉; 大和田 謙二; 吉田 雅洋; Jarrige, I.; 多々見 央*; et al.

Physical Review B, 83(24), p.241101_1 - 241101_4, 2011/06

 被引用回数:20 パーセンタイル:30.89(Materials Science, Multidisciplinary)

We report a Cu $$K$$-edge resonant inelastic X-ray scattering (RIXS) study of orbital excitations in KCuF$$_3$$. By performing the polarization analysis of the scattered photons, we disclose that the excitation between the $$e_g$$ orbitals and the excitations from $$t_{2g}$$ to $$e_g$$ exhibit distinct polarization dependence. The polarization dependence of the respective excitations is interpreted based on a phenomenological consideration of the symmetry of the RIXS process that yields a necessary condition for observing the excitations. In addition, we show that the orbital excitations are dispersionless within our experimental resolution.


Contribution of intermediate submicrometer structures to physical properties near $$T$$$$_{rm c}$$ in Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9%PbTiO$$_{3}$$PbTiO$$_{3}$$

大和田 謙二; 水木 純一郎; 並河 一道*; 松下 三芳*; 下村 晋*; 中尾 裕則*; 廣田 和馬*

Physical Review B, 83(22), p.224115_1 - 224115_7, 2011/06

 被引用回数:7 パーセンタイル:62.55(Materials Science, Multidisciplinary)



高分解能X線非弾性散乱実験と計算機実験によるPb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$の研究; 反強誘電状態からリラクサーまでを制御するBサイトランダムネスの効果

大和田 謙二; 富田 裕介*

日本物理学会誌, 65(10), p.800 - 804, 2010/10



X-ray photon correlation spectroscopy study in valence fluctuation compound Eu$$_{3}$$S$$_{4}$$

中尾 裕則*; 大和田 謙二; 下村 晋*; 落合 明*; 並河 一道*; 水木 純一郎; 三村 秀和*; 山内 和人*; 村上 洋一*

AIP Conference Proceedings 1234, p.935 - 938, 2010/06

 被引用回数:2 パーセンタイル:29.02

X-ray photon correlation spectroscopy (XPCS) is a powerful tool to perform direct measurements of the dynamics of fluctuations in condensed matter systems at atomic resolution. Here we have investigated spatial and time correlations of domains in the valence fluctuated phase in a typical valence fluctuation compound Eu$$_{3}$$S$$_{4}$$ near the charge ordering temperature ($$T_{CO}$$). The spatial correlation was observed at the fundamental reflection (4 4 4) using coherent diffraction techniques, which indicated that the domain size is longer than 200 nm near $$T_{CO}$$. The time correlation of the domain was measured by the XPCS technique, and we found that the slow fluctuation of the order of 10 second exists only near $$T_{CO}$$.


Powder X-ray diffraction study of Ne up to 240 GPa

竹村 謙一*; 綿貫 徹; 大和田 謙二; 町田 晃彦; 大村 彩子*; 青木 勝敏

Journal of Physics; Conference Series, 215, p.012017_1 - 012017_4, 2010/03

 被引用回数:13 パーセンタイル:2.81



X-ray intensity fluctuation spectroscopy using nanofocused hard X-rays; Its application to study of relaxor ferroelectrics

大和田 謙二; 並河 一道*; 下村 晋*; 中尾 裕則*; 三村 秀和*; 山内 和人*; 松下 三芳*; 水木 純一郎

Japanese Journal of Applied Physics, 49(2), p.020216_1 - 020216_3, 2010/02

 被引用回数:3 パーセンタイル:82.81(Physics, Applied)

The use of a combination of coherent X-rays from a third-generation synchrotron light source and ultraprecise Kirkpatrick-Baez mirrors enables us to apply nanofocused hard X-rays in solid-state physics. We developed an apparatus for X-ray intensity fluctuation spectroscopy using the nanofocused hard X-rays and applied it to the study of relaxor ferroelectrics. We have successfully detected a large and slow intensity fluctuation of scattered X-rays above cubic-to-tetragonal phase transition temperature with a characteristic time scale on the order of 10 s. We speculated that the intensity fluctuation originates from domain number fluctuation, which is directly related to the dielectric response, particularly the frequency dispersion.

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