Anomalous low-energy phonons in nearly tetragonal BiFeO3 thin films

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.

arXiv comment4 pages, 5figures

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Cited by in corpus (3)

• A multiferroic on the brink: uncovering the nuances of strain-induced transitions in BiFeO${}_3$
• Temperature and thickness evolution and epitaxial breakdown in highly-strained BiFeO3 thin films
• Strain-gradient-induced magnetic anisotropy in straight-stripe mixed-phase bismuth ferrites: An insight into flexomagnetic phenomenon