Oblique Phonons with Special Concern to the Soft Phonon in Tetragonal BaTiO3

Abstract

Raman spectra of oblique phonons in a tetragonal BaTiO3 single crystal were obtained for different angle 0 which the phonon wavevector q makes with the c-axis. A complete analysis of the data has been made on the basis of Merten�s equation. The spectrum of the oblique phonon on the branch that runs from the overdamped soft E(x)TO phonon to the underdamped 175 cm-1 A1(z)TO phonon has been found to show a peak in the range 0=30�. This result provides a new method of obtaining the temperature dependence of the overdamped soft phonon. © 1983, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.