Quantum paraelectric SrTiO3 shows the ferroelectricity by the exchange of 16O for its isotope 18O. Raman scattering experiment is performed on the isotopically exchanged SrTi(O0.32 16 18O0.68)3 whose exchange rate is just below the critical exchange rate. Raman spectrum of ferroelectric soft mode in the paraelectric phase clearly indicates local symmetry-breaking induced by the 18O-exchange. The temperature dependence of the soft mode in SrTi(O0.32 16 18O0.68)3 suggests the occurrence of local ferroelectric region before the onset of the ferroelectric phase. The inhomogeneity of the system induces the inhomogeneous softening of the soft mode in 18O-exchanged SrTiO3.
Acknowledgment
The present study is partially supported by a Grant-in-Aid for JSPS Fellows, a Grant-in-Aid for Scientific Research (A) from JSPS No. 14204029, and a Grant-in-Aid for Young Scientists (A) from MEXT No. 14702006.
Paper originally presented at IMF-11, Iguassu Falls, Brazil, September 5–9, 2005