Evidence for competing orderings in strontium titanate from hyper-Raman scattering spectroscopy
Research Institute for Electronic Science, Hokkaido University
Kita-ku, Sapporo 060-0812, Japan
2 Laboratoire des Verres, UMR 5587 CNRS, Université Montpellier 2 F-34095 Montpellier Cedex 5, France
Accepted: 5 April 2000
The frequencies of the softest polar optic phonons of tetragonal SrTiO3 are accurately determined using high-resolution hyper-Raman spectroscopy on oriented-domain crystals. The splitting of the polar soft mode in the tetragonal phase is quantitatively related to the 105 K structural transition, i.e., to the rotation of the oxygen octahedra and to the associated macroscopic strains. In addition to quantum fluctuations, these tetragonal distortions are found to be essential in preventing the ferroelectric transition.
PACS: 77.84.Dy – Niobates, titanates, tantalates, PZT ceramics, etc / 64.90.+b – Other topics in equations of state, phase equilibria, and phase transitions / 78.35.+c – Brillouin and Rayleigh scattering; other light scattering
© EDP Sciences, 2000