Dielectric response of the domain wall structure in KH2PO4-type crystals below “freezing” temperature

Abstract

Abstract Within the assumption that the domain walls are localized (below the freezing temperature) we have theoretically investigated the linear response of the domain structure making use of Bloch equations and a pseudospin model Hamiltonian appropriate to KH2PO4-type crystals. Our results concerning the frequency and temperature dependent dielectric susceptibility reveal the multirelaxational type behaviour of the wall dynamics. The domain walls contribute to the dielectric response of the crystal at lower frequencies than the soft mode. At the same time the relaxation frequency of localized walls is higher as compared to the low-frequency response observed in experiments. The contribution of domain walls depends on the amount of the walls in the sample. The temperature and frequency dependent dielectric susceptibility obtained for the case of polydomain crystals is suitable for experimental verification of the model assumptions about the localization of the domain walls below the “freezing” temperature.