Dynamical properties of guest ions in the type-I clathrate compounds X8Ga16Ge30 (X=Eu,Sr,Ba) investigated by Raman scattering
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ID | 19288 |
本文ファイル | |
著者 |
Takasu, Yuichi
Avila, Marcos A.
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抄録(英) | Raman active phonons in the type-I clathrate compounds of X8 Ga16 Ge30 (X=Eu,Sr,Ba) have been fully assigned by the combination of polarized Raman scattering and first principles calculations. The dynamical motions of guest ions in the 6d -site cage have been clearly identified. The energy of the modes, related to a rattling motion, decreases with decreasing temperature. The energy-decrease at low temperatures is a common property for thermal rattling in X8 Ga16 Ge30. The anomalous decreases are originated from the quartic anharmonic potential, and its contribution has been experimentally determined. A mixed state between thermal rattling and quantum tunneling has been observed below 10 K. A soft mode due to the guest ion motion has been observed, but the transition due to this soft mode is somewhat different from the ordinary structural transition because of the shielding by carriers. In addition, it is found that the elastic dispersion of Sr8 Ga16 Ge30 is caused by the interference with the rattling motion of the guest ion in the cage, and that the rattling at the off-center location plays an important role to suppress a lattice thermal conductivity and to achieve the phonon-glass state in X8 Ga16 Ge30.
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掲載誌名 |
Physical Review B - Condensed Matter and Materials Physics
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巻 | 74巻
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号 | 17号
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開始ページ | 174303-1
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終了ページ | 174303-5
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出版年月日 | 2006-11-22
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出版者 | American Physical Society
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ISSN | 1098-0121
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NCID | |
出版者DOI | |
言語 |
英語
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NII資源タイプ |
学術雑誌論文
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広大資料タイプ |
学術雑誌論文
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DCMIタイプ | text
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フォーマット | application/pdf
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著者版フラグ | publisher
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権利情報 | Copyright (c) 2006 The American Physical Society.
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関連情報URL | |
部局名 |
総合科学研究科
先端物質科学研究科
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