Abstract
The in-plane and out-of-plane ferroelectric instabilities in compressed (100)-epitaxial films were examined by infrared reflection spectroscopy. The strongly stiffened in-plane soft mode frequency softened very slowly on cooling. On the other hand, the silent mode appeared at around 150 K, indicating an out-of-plane ferroelectric transition. This behavior points to a split of in-plane and out-of-plane ferroelectric instability temperatures due to the lowered symmetry of the lattice caused by mechanical misfit strain. Infrared spectroscopy provides a possibility to detect such an effect in the strained epitaxial ferroelectric films.
- Received 20 January 2006
DOI:https://doi.org/10.1103/PhysRevLett.96.157602
©2006 American Physical Society