Broad Doublet Spectra and Anomalous Light Scatterings in Quantum Paraelectric States of SrTiO₃ and Nb-Doped SrTiO₃

Abstract

The 180° light scattering experiment has been performed with the SrTiO ₃ , 0.02 wt% Nb-doped SrTiO ₃ , and 0.05 wt% Nb-doped SrTiO ₃ samples. The broad doublet is found to become weaker with increasing Nb-concentration. Furthermore, the total scattering intensity is found to show the anomalous behavior below T _q = 37 K in the SrTiO ₃ and 0.02 wt% Nb-doped SrTiO ₃ samples. These results strongly suggest that there exist the ferroelectric regions in these materials with the length-scale of the order of 100 nm below T_q.

Keywords:

• SrTiO₃
• Nb-doped SrTiO₃
• broad doublet
• length-scale
• quantum paraelectrics
• light scattering

PACS numbers:

• 64.60.Ht
• 77.80.-e
• 77.84.Dy
• 78.35.+c

Acknowledgments

The authors express their appreciation to Mr. Takao Ohta for his polishing the samples so as to have the optical grade surfaces. The present work has been supported in part by a Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Science, Sports and Culture of Japan, No. 19540325.