Central peak in the strontium titanate crystal near the tetragonal-to-cubic phase transition

Abstract

Raman spectra of the SrTiO3 crystal have been measured in wide temperature (22–316 K) and frequency (2–1020 cm−1) ranges. It has been shown that a central peak appears in low-frequency Raman spectra at temperatures above 70 K. In the spectral geometry with polarization rotation near the temperature Tc = 106 K of the cubic-to-tetragonal phase transition, the central peak exhibits properties of the order-disorder phase transition. Such a behavior of the central peak has been explained by the interaction of the low-frequency soft mode Eg with the relaxation mode near Tc.