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論文

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

https://doi.org/10.1063/1.4921847

被引用回数：39 パーセンタイル：81.4(Physics, Applied)

The local atomic structures around Co in high temperature diluted ferromagnetic semiconductor Co-doped TiO 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 simply substituted for Ti sites in the rutile structure, a suboxidic arrangement of CoOTi was found to form around Co in the Ti $_{0.95}$ Co $_{0.05}$ O films. First-principles calculations supported the stability of the aggregated suboxidic clusters in the rutile TiO. The suboxidic coordination may be the source of strong exchange interaction, resulting in the high Curie temperature in Co-dopedTiO.

論文

Anomalous temperature dependence of current-induced torques in CoFeB/MgO heterostructures with Ta-based underlayers

Kim, J.*; Sinha, J.*; 三谷誠司*; 林将光*; 高橋三郎*; 前川禎通; 山ノ内路彦*; 大野英男*

Physical Review B, 89(17), p.174424_1 - 174424_8, 2014/05

https://doi.org/10.1103/PhysRevB.89.174424

被引用回数：93 パーセンタイル：93.96(Materials Science, Multidisciplinary)

磁気トンネル接合素子に用いられるCoFeB/Mgoヘテロ構造膜の下地に用いられるTa膜の影響を調べた。Ta下地膜は電流による磁化反転に大きな効果を持っていることがわかった。この結果はスピン拡散モデルで解析された。

論文

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

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

https://doi.org/10.1103/PhysRevB.89.140103

被引用回数：48 パーセンタイル：85.87(Materials Science, Multidisciplinary)

The local structures around Nb and Pb in the relaxor ferroelectric Pb(Mg $_{1/3}$ Nb $_{2/3}$ )O 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 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.

論文

Time-domain observation of the spinmotive force in permalloy nanowires

林将光*; 家田淳一; 山根結太; 大江純一郎*; 高橋有紀子*; 三谷誠司*; 前川禎通

Physical Review Letters, 108(14), p.147202_1 - 147202_5, 2012/04

https://doi.org/10.1103/PhysRevLett.108.147202

被引用回数：37 パーセンタイル：82.07(Physics, Multidisciplinary)

磁壁移動に伴うスピン起電力を、パーマロイ細線における通常の誘導起電力を適切に差し引いた実時間電圧測定により直接検出する。磁壁の移動速度は印加磁場の大きさに対して非線形な振る舞いを示すが、出力電圧は磁場に対して線形となる。電圧信号の符号は、磁壁の運動方向に応じて反転することが示される。これらの振る舞いは、数値シミュレーションにより定量的に説明され、磁壁運動が周期的な磁化構造変化によって特徴付けられないような磁場領域にあったとしても、出力が外部磁場に対して線形に応答する様子が示される。

報告書

HTTR水素製造システム実規模単一反応管試験装置の機能試験結果報告(受託研究)

稲垣嘉之; 林光二; 加藤道雄; 藤崎勝夫; 会田秀樹; 武田哲明; 西原哲夫; 稲葉良知; 大橋弘史; 片西昌司; et al.

JAERI-Tech 2003-034, 129 Pages, 2003/05

JAERI-Tech-2003-034.pdf:7.62MB

HTTR水素製造システムの中間熱交換器から下流の水素製造設備を模擬した実規模単一反応管試験装置の機能試験の結果について報告する。本試験装置は、HTTR水素製造システムの水蒸気改質器反応管1本を実寸大で模擬した装置で、熱源には原子炉の代わりに電気ヒータを用いて、HTTR水素製造システムと同じ温度・圧力の条件で試験を行うことができる。試験装置は、平成9年より設計,製作を開始し、平成13年9月に据付を完了した。平成13年10月から平成14年2月まで実施した機能試験において、各設備の性能確認を行うとともに、高温ヘリウムガスを熱源として120m $^{3}$ N/hの水素製造を達成して、試験装置を完成させた。また、本報告では、機能試験時に発生した不具合事項とその対策についても合わせて述べる。

報告書

HTTR水素製造システム実規模単一反応管試験装置のヘリウムガス循環機の性能確認試験結果(受託研究)

清水明; 加藤道雄; 林光二; 藤崎勝夫; 会田秀樹; 武田哲明; 西原哲夫; 片西昌司; 高田昌二; 稲葉良知; et al.

JAERI-Tech 2003-033, 105 Pages, 2003/03

JAERI-Tech-2003-033.pdf:8.35MB

HTTR水素製造システムのモックアップモデルとして建設した「実規模単一反応管試験装置」のヘリウムガス循環機に付き、2001年度に実施した総合機能試験結果を解析し、その特性を述べた。試験データを解析し、昇温値,電力,昇温値に関する性能曲線を求めた。また、これらの性能曲線を使い「循環機性能予測計算コード」を作成した。さらに、ヘリウムガス供給系主循環設備の全体圧力損失を評価した。ヘリウムガス循環機は、試験において圧力2.7MPa~4.0MPa,流量250g/s~400g/s,昇温値~250kPaの運転が必要となるが、最大入力電力150kW,最大回転数12,000rpm以内という循環機運転制限値内で達成できることが確認できた。

論文

Pseudomorphic growth of Pd monolayer on Au(111) electrode surface

高橋正光; 林由紀雄; 水木純一郎; 田村和久*; 近藤敏啓*; 猶原秀夫*; 魚崎浩平*

Surface Science, 461(1-3), p.213 - 218, 2000/08

https://doi.org/10.1016/S0039-6028(00)00583-5

被引用回数：71 パーセンタイル：91.97(Chemistry, Physical)

Au(111)上に塩化パラジウム酸溶液から電析したPd単原子層の構造を表面X線回折法で解析した。鏡面反射条件と非鏡面反射条件の両方で、逆格子ロッドに沿った強度分布を測定することにより、面内方向と表面垂直方向についての構造情報を得ることができた。その結果によれば、Au(111)電極表面では、Pdは基板原子の積層秩序を引き継いだ、平坦な原子層を形成する。このようなPd層が安定に存在する理由としては、溶液中のイオンとの相互作用や、電析中のAu表面の原子配列の影響が考えられる。Pd/Au(111)界面におけるPd-Au間の結合長は、それぞれのバルク中でのPdとAuの原子半径の和にたいへん近い。

口頭

Direct observation of higher order atomistic structure in Ti $_{50}$ Ni $_{44}$ Fe $_{6}$ at lower temperature phase

Hu, W.; 林好一*; 八方直久*; 細川伸也*; 寺井智之*; 福田隆*; 掛下知行*; 高橋正光

no journal, ,

The Ti-Ni series shape memory alloys shows novel phase transition behaviours depending on the concentrations of doped third element Fe and only the precursor phenomena are observed when more than 6 at.% of Fe atoms are substituted for Ni. In the present work, we have focused on Ti $_{50}$ Ni $_{44}$ Fe $_{6}$ , which exhibits only a second-order-like parent (P) - incommensurate (IC) - commensurate (C) transition, and investigated the local structure around Fe and Ni by the X-ray fluorescence holography (XFH). We successfully obtained 3D real space local structures at both the P- and C-phases. Cluster-like structure appears around Fe and the direct evidence of the existence of supperlattice structure at C-phase appears around Ni. We discuss structural changes by comparing the microstructures obtained around Fe and Ni at two phases. The results provide hints on the lattice modulation related to precursors of the martensitic transition and direct evidence of superlattice phenomena.

口頭

Direct observation of local structure distortion in Pb(Mg $_{1/3}$ Nb $_{2/3}$ )O $_{3}$ by X-ray fluorescence holography

Hu, W.; 林好一*; 八方直久*; 大和田謙二; Chen, J.*; Ye, Z.-G*; 細川伸也*; 高橋正光

no journal, ,

The chemical ordering regions (CORs) and polar nanoregions (PNRs) in relaxor ferroelectrics have been long believed to the origin of their high and temperature-independent permittivities. In the present work, we carried out X-ray fluorescence holography (XFH) experiments of Pb(Mg $_{1/3}$ Nb $_{2/3}$ )O $_{3}$ (PMN) and La-doped PMN (2 at% La, PLMN) single crystals, which are prototype relaxor ferroelectric material, and investigated the local structure around Nb atoms at BL22XU of SPring-8. The La-doped PMN single crystal shows much bigger CORs than pure PMN. Nb K (16.6 keV) fluorescent X-rays were analyzed and focused on an avalanche photodiode detector with a cylindrical graphite-crystal energy analyzer. The results indicate that both Pb-site and Mg/Nb-site atoms have big fluctuations in PMN system and 1st neigher Pb atoms tend to shift toward central Nb atom along [111] direction.

口頭

Precursor phenomena of martensitic transformation in Fe-doped Ti-Ni alloys studied by X-ray fluorescence holography

Hu, W.; 林好一*; 八方直久*; 寺井智之*; 福田隆*; 掛下知行*; 高橋正光

no journal, ,

The gradual changes in the lattice modulation, phonon dispersion and elastic modulus, which are attracting much interest as precursors of the martensitic transition, have been experimentally reported for many materials. However, studying the precursors is difficult because they are immediately followed by the main martensitic transition. Ti $_{50}$ Ni $_{44}$ Fe $_{6}$ , which shows only parent - incommensurate - commensurate phase transition, is a suitable sample for investigating the lattice modulation accompanied by the appearance of the superlattice structure. In the present work, X-ray fluorescence holography technique have been applied for investigating the 3D local structure around Fe and Ni at both the parent and commensurate phases. We will discuss the dynamical structural changes at both phases, and the results will provide hints to the lattice modulation related to precursors of the martensitic transformation.

口頭

3D local structure analysis of relaxor ferroelectrics by X-ray fluorescence holography

Hu, W.; 林好一*; 八方直久*; 大和田謙二; Chen, J.*; Ye, Z.-G*; 細川伸也*; 高橋正光

no journal, ,

Relaxor ferroelectrics as a class of disordered crystals possessing peculiar structure and properties have attracted significant research attention. However, quantitative analysis of its local structure and lattice distortion is difficult by conventional diffraction methods. In the present work, the authors carried out X-ray fluorescence holography experiments on PMN and La-doped PMN (PLMN) single crystals at BL22XU of SPring-8 and successfully obtained 3D atomic images around Nb and Pb elements up to 20 with atomic resolution, respectively. The local distortion of Pb atoms was directly revealed by comparing the atomic images with the reference sample SrTiO $_{3}$ (ideal perovskite structure). We will discuss the differences between PMN and PLMN by comparing the obtained middle range local structures around Nb and Pb, and the pure structure of the chemical ordered domains on the atomic scale.

口頭

蛍光X線ホログラフィーによるPb(Mg $_{1/3}$ Nb $_{2/3}$ )O $_{3}$ リラクサー強誘電体の三次元局所構造解析

Hu, W.; 林好一*; 八方直久*; 大和田謙二; Chen, J.*; Ye, Z.-G*; 細川伸也*; 高橋正光

no journal, ,

Relaxor ferroelectrics as a class of disordered crystals possessing peculiar structure and properties have attracted significant research attention. However, quantitative analysis of its local structure and lattice distortion is difficult, and there is no report to our knowledge of direct observation of its three-dimensional local structure. In the present work, we carried our X-ray fluorescence holography experiments on Pb(Mg $_{1/3}$ Nb $_{2/3}$ )O $_{3}$ (PMN) single crystal at BL22XU of SPring-8 and successfully obtained 3D atomic images around Nb and Pb elements up to 2 nm with atomic resolution. Our result shows the direct evidence of the rhombohedral distortion in PMN. Comparing with theoretical calculation, coexistence of two rhombohedral distortions was confirmed. In this presentation, we will discuss the short-range distortion of Pb atoms by comparing the obtained 3D atomic images around Nb at room temperature and 100 K.