Central Peak in SrTi¹⁸O₃ Studied by Light Scattering

Abstract

A central peak (CP) has been found mainly in the VH light scattering spectra of SrTi(¹⁸ O _0.87 ¹⁶ O _0.13)₃ (87% ¹⁸O-exchanged SrTiO₃). Both of the intensity and relaxation time of the CP show broad peaks around T _m ≈ 22 K (below the transition temperature T _c ≈ 25 K). The physical origin of the CP is determined not to be the polarization fluctuation, representing that this CP is not a sign of a phase transition of order-disorder type. The stochastic fluctuation of the spatial derivatives of the polarization would be the physical origin of the CP.

Keywords:

• SrTi¹⁸O₃
• ferroelectricity
• phase transition
• light scattering
• central peak

Acknowledgments

The authors express their appreciation to Professor Toshirou Yagi for his valuable experimental advices and to Mr. Tatsuji Meike for his continual improvement of the light scattering cell. The present work has been supported in part by a Grant-in-Aid for Scientific Research (B) from the Ministry of Education, Science, Sports and Culture of Japan, No. 14340086.