New Dielectric Resonances in Mesoscopic Ferroelectrics

Abstract

A new type of dielectric resonance has been observed in several mixed ferroelectrics, ${\mathrm{KTa}}_{1\ensuremath{-}x}{\mathrm{Nb}}_{x}{\mathrm{O}}_{3}$ (KTN), ${\mathrm{K}}_{1\ensuremath{-}x}{\mathrm{Li}}_{x}{\mathrm{TaO}}_{3}$ (KLT), and ${\mathrm{PbMg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_{3}$ (PMN), also known as relaxor ferroelectrics. This resonance and its metastability (persistence over long periods of time) in KTN in the paraelectric phase provides clear evidence, in relaxors, for the presence of permanent polar nanoregions and strong polarization-strain coupling. The frequencies calculated from the elastic constant reveal the unexpected clamped nature of the resonance. These results point to the essential role of polar regions in the relaxor behavior.