DIELECTRIC STUDIES IN T-ASTERISK AND T' STRUCTURES OF (LA,GD)(2)CUO4

The real (epsilon') and imaginary (epsilon '') parts of dielectric con stant in some T* (La1.15Gd0.85CuO4) and T' (La0.3Gd1.7CuO4) copper-oxi de samples were investigated as a function of temperature (15-300 K) a nd frequency (10(2)-10(6) Hz). The epsilon' reveals a very gigantic va lue at low frequencies in both cases. These two T* and TI samples show a thermally activated process with a small activation energy of 0.034 eV for T* sample and 0.044 eV for T' sample, respectively. We have fo und cu value of 0.11 for the T* sample at 50 K and 0.48 for the T' sam ple at 60 K. These temperature and frequency effects in epsilon', epsi lon '' and sigma can be nicely interpreted in terms of dipole polariza tion associated with the 3D hopping motion of localization charge cent ers. (C) 1998 Elsevier Science B.V. All rights reserved.