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

doi:10.1103/PhysRevB.84.132408

Anomalous low-energy phonons in nearly tetragonal BiFeO3 thin films

Strongly Correlated Electrons 2015-05-30 v1

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

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Abstract

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.

Keywords

BiFeO3 thin films ferroelectric transformation low-energy phonons Raman scattering octahedron tilting multiferroic

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@article{arxiv.1108.4484,
  title  = {Anomalous low-energy phonons in nearly tetragonal BiFeO3 thin films},
  author = {K. -Y. Choi and S. H. Do and P. Lemmens and D. Wulferding and C. S. Woo and J. H. Lee and K. Chu and C. -H. Yang},
  journal= {arXiv preprint arXiv:1108.4484},
  year   = {2015}
}

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4 pages, 5figures

Anomalous low-energy phonons in nearly tetragonal BiFeO3 thin films

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