温度によって引き起こされるA-Bサイト間電荷移転は,AサイトでオーダーされたLaCu(3)Fe(4)O(12) ペロブスキートで起こります
1Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan. ywlong@msk.kuicr.kyoto-u.ac.jp
Nature
|March 6, 2009
まとめ
研究者らは,LaCu(3) Fe(4) O(12) の温度によるバレンスの変化を発見した. この移行は,サイト間での電荷移転を含み,負の熱膨張を含む構造的,磁的,電気的性質の重要なシフトにつながります.
科学分野:
- マテリアルサイエンス 材料科学
- 固体化学 固体化学
- 凝縮物質物理学 凝縮物質物理学
背景:
- 移行金属酸化物のバレンスの状態の変化は,構造的および物理的性質を大幅に変化させます.
- 化学ドーピングは,バレンスの状態を調節するための標準的な方法であり,しばしば ABO ((3) ペロブスキートのエキゾチックな性質につながります.
- 外部から誘発された電荷移転によるバレンスの変化はまれで,通常は極端な条件を必要とします.
研究 の 目的:
- 温度によって引き起こされるバレンスの変化と,A-サイトでオーダーされた二重ペロブスキートにおけるサイト間電荷移転を調査する.
- 構造的,磁的,および輸送特性における結果として生じる修正を調査する.
- 技術の応用の可能性を評価し,特に負の熱膨張に焦点を当てます.
主な方法:
- A位点配列のダブルペロブスキットLaCu(3)Fe(4)O(12) の合成と特徴付け.
- 気温に依存する測定法で,相変化や性質の変化を観察する.
- ヴァレンスの状態とサイト間電荷移転機構の分析.
主要な成果:
- 393 Kで,A位 (Cu) とB位 (Fe) のイオンの両方のバレンスの変化を含む,第一位,可逆的な移行が観察されました.
- CuとFeの間のサイト間電荷の移転が特定され,LaCu(2+) ((3) Fe ((3.75+) ((4) O ((12) からLaCu(3+) ((3) Fe ((3+) ((4) O ((12) に移行しました.
- パラマグネティックからアンチフェロマグネティック,メタリックから絶縁状態への相対構造の相変遷が実証され,大きな負の熱膨張が伴います.
結論:
- LaCu ((3) Fe ((4) O ((12)) は,独特の温度によるバレンスの変化と,場所間での電荷移転を示しています.
- これらの変化は,磁気,電気,構造の性質に重大な,結合された変化をもたらします.
- 陰性熱膨張の観測された室温以上の温度移行は,技術的な応用にとって有望である.
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