ANOMALOUS DIELECTRIC-RELAXATION IN LITHIUM-POTASSIUM TANTALATE CRYSTALS

In order to describe the unusual dielectric properties observed in K1- xLixTaO3 crystals a ne- approach is proposed. The dynamical Glauber th eory, previously applied to spin-glasses, is modified by the introduct ion of the spectral distribution of the random interactions between th e dipoles associated with the Li+ ions. Moreover, the dipole correlati ons are taken into account by the Onsager reaction field. As a result, the calculated dielectric constant reproduces well the unusual featur es of the Argand diagrams and, in particular, their finite slope at lo w frequencies and infinite slope at high frequencies (strophoidal shap e). The temperature dependence of some parameters shows, however, the limits of a spin-glass type model in describing the collective behavio ur of randomly distributed dipoles in a highly polarizable medium.