The role of polar-nanoregions in KTa_1-xNb_xO₃ single crystals studied by Raman scattering

ABSTRACT

The dynamical properties of KTa_1-xNb_xO₃ (x = 0.40) crystals were investigated by Raman scattering. The remarkable change of the central peak (CP) intensity was observed in the vicinity of T_C. The physical origin of the CP in the cubic phase caused by the fluctuating polar nanoregions (PNRs) with A₁(z) symmetry was discussed using the results of the angular dependence of Raman scattering. The phase difference between different Raman tensor components related to PNRs with the A₁(z) symmetry was observed. The local symmetry breaking in the cubic phase was discussed on the basis of the evolution of the PNRs.

KEYWORDS:

• Raman scattering
• polar nanoregions
• perovskite
• KTN

Acknowledgments

This work was supported in part by the Marubun research promotion foundation and the JSPS KAKENHI Grant Number 90134204. The authors thank to Mr. M. A. Helal for his support of the Raman measurements and discussion.To set up the angular dependence of Raman scattering system, the authors also thank to Dr. Fuji for his technical support.