Relaxor ferroelectrics and intrinsic inhomogeneity

Relaxor ferroelectrics (RF) are characterized by diffuse ferroelectric transitions and high and frequency-dependent dielectric susceptibilities. Non-RFs show high dielectric responses only in the direct vicinity of the transition temperature whereas RFs exhibit high responses over a large temperature range. Despite their long history, the microscopic origin of RFs is still unknown due to their structural complexity. RF behaviour is exclusively observed in nonstoichiometric, mixed ion systems, and represents a composite of dielectrically soft matrix and highly polarizable doped ions. Here we propose a multi-component scenario with intrinsic inhomogeneity, which shows that spatially localized excitations (discrete breathers) coupled to the soft matrix yield a self-consistent multi-length scale response and successfully explains the relaxor ferroelectric behaviour.