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arXiv 1108.4484cond-mat.str-el
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近四重态BiFeO3薄膜中的反常低能声子

Anomalous low-energy phonons in nearly tetragonal BiFeO3 thin films

K. -Y. Choi, S. H. Do, P. Lemmens, D. Wulferding, C. S. Woo, J. H. Lee, K. Chu, C. -H. Yang

摘要:

我们提出了一个伴随的结构和铁电转变周围的$T_S\sim 360$ K多铁性BiFeO $_3$ /LaAlO $_3$薄膜接近的tetraphy相的证据。利用拉曼散射研究了声子激发随温度的变化。在180-260 cm $^{-1}$处与FeO $_6$八面体倾斜相关的低能声子模式在通过$T_S$冷却时显示出异常行为;(i)高达15 cm $^{-1}$的大硬化,(ii)强度增加一个数量级,以及(iii)十几个新模式的出现。与此相反,高频模式只表现出弱异常。这表明八面体倾斜与铁电性的密切耦合导致结构和铁电性质的同时变化。

英文摘要:

We present evidence for a concomitant structural and ferroelectric transformation around $T_S\sim 360$ K in multiferroic BiFeO$_3$/LaAlO$_3$ thin films close to the tetragonal phase. Phonon excitations are investigated by using Raman scattering as a function of temperature. The low-energy phonon modes at 180-260 cm$^{-1}$ related to the FeO$_6$ octahedron tilting show anomalous behaviors upon cooling through $T_S$; (i) a large hardening amounting to 15 cm$^{-1}$, (ii) an increase of intensity by one order of magnitude, and (iii) an appearance of a dozen new modes. In contrast, the high-frequency modes exhibit only weak anomalies. This suggests an intimate coupling of octahedron tilting to ferroelectricity leading to a simultaneous change of structural and ferroelectric properties.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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