Abstract
We measured the Raman spectra of ferroelectric Sn-doped SrTiO3, (Sr1-aSna)(Ti1-bSnb)O3 (x = a + b = 0.1, 0.05 and 0.02) in the temperature range from 300 to 20 K. At room temperature, polar transverse optic modes were observed; which are forbidden in Oh cubic symmetry. The soft mode showed no freezing but remained at constant frequency; it split into two peaks at low temperature. Several modes became active through zone folding below 150 K. Instead of freezing of the soft mode, a relaxation mode related to ferroelectricity was found in the low frequency region.
Acknowledgment
The authors thank K. Deguchi and H. Kasatani for their helpful discussions.