Collective Dynamics of Off-Center Ions inK1−xLixTaO3: A Model of Relaxor Behavior

Abstract

The relaxor behavior is characteristic of the class of disordered ferroelectrics. These systems possess a high dielectric constant with a broad relaxation peak and a low frequency dispersion. Because of their complexity, there exist various explanations for their dielectric and polarization behavior, but no unifying model. In the present paper we show that the simpler system, ${\mathrm{K}}_{1-x}{\mathrm{Li}}_x\mathrm{Ta}{\mathrm{O}}_3$, is also a relaxor and a generic one at that. We describe its dynamical behavior with a general microscopic model and show that the relaxor behavior is intrinsically due to the dipolar interaction between randomly distributed off-center ions mediated by a highly polarizable lattice.