Temperature Dependence of the Raman Frequency, Damping Constant and the Activation Energy of a Soft-Optic Mode in Ferroelectric Barium Titanate
Abstract
The Raman frequency of a soft-optic mode associated with the order parameter is calculated as a function of temperature from the mean field theory for barium titanate (TC=222 K). Using the Raman frequencies calculated, the damping constant is evaluated and it is compared with the observed one for this soft-optic mode. Using the temperature dependence of the damping constant which is calculated from the pseudospin-phonon coupled model and from the energy fluctuation model, activation energies are also deduced for the soft-optic mode of barium titanate. For the temperatures to 330 K, the activation energy U varies from 0.03 to 0.01 eV, which can be compared with the value of kBTC≅ 0.02 eV. Above 330 K, it decreases as predicted from both models. It is shown here that the calculated Raman frequency and the damping constant of the soft-optic mode describe adequately the observed behaviour of barium titanate. The activation energies deduced are also reasonable.
- Publication:
-
Ferroelectrics
- Pub Date:
- January 2012
- DOI:
- Bibcode:
- 2012Fer...432...14K
- Keywords:
-
- Raman frequency;
- damping constant;
- activation energy;
- barium titanate
