Structural instability of the CoO4 tetrahedral chain in SrCoO3−δ thin films

Raman scattering experiments together with detailed lattice dynamic calculations are performed to elucidate crystallographic and electronic peculiarities of SrCoO3−δ films. We observe that the 85 cm−1 phonon mode involving the rotation of a CoO4 tetrahedron undergoes a huge hardening by 21 cm−1 with...

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Bibliographic Details
Published in:Journal of applied physics 2015-08, Vol.118 (8)
Main Authors: Glamazda, A., Choi, K.-Y., Lemmens, P., Choi, Woo Seok, Jeen, Hyoungjeen, Meyer, Tricia L., Lee, Ho Nyung
Format: Article
Language:English
Subjects:
Applied physics
Brownmillerite
Calcium aluminum ferrite
Chains
Crystallography
Jahn-Teller effect
Lattice vibration
MATERIALS SCIENCE
Phonons
Raman spectra
Structural stability
Thin films
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Summary:Raman scattering experiments together with detailed lattice dynamic calculations are performed to elucidate crystallographic and electronic peculiarities of SrCoO3−δ films. We observe that the 85 cm−1 phonon mode involving the rotation of a CoO4 tetrahedron undergoes a huge hardening by 21 cm−1 with decreasing temperature. In addition, new phonon modes appear at 651.5 and 697.6 cm−1. The latter modes are attributed to the Jahn-Teller activated modes. Upon cooling from room temperature, all phonons exhibit an exponential-like increase of intensity with a characteristic energy of about 103–107 K. We attribute this phenomenon to an instability of the CoO4 tetrahedral chain structure, which constitutes a key ingredient to understand the electronic and structural properties of the brownmillerite SrCoO2.5.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4929659