Influence of External Fields on the Properties of SrTi(16 O1–x18 Ox)3 at Oxygen Isotope Substitution∗.

The dynamic mechanism of the ferroelectric phase transition in SrTi(16O1-x18Ox)3induced by the isotope exchange of18O for16O is proposed. This mechanism is based on the electron-lattice p-d coupling, TO and TA phonon-phonon interactions and the quantum fluctuations (zero-point motion). The lowest zone center modeF1u(Γ) in the cubic phase splits intoA2u+Eumodes in the tetragonal phase and theEumode is the ferroelectric soft mode in SrTi18O3. It is shown that the application of hydrostatic pressure on the ferroelectric SrTi18O3depresses the transition temperature down to 0 K abovepc≈0.7 kbar through the electron-lattice strain coupling.∗Paper Originally Presented at 10th European Meeting on Ferroelectricity, Cambridge, U.K., August 3–8, 2003. E-mail:konsin@fi.tartu.ee [ABSTRACT FROM AUTHOR]