ELECTRIC-FIELD GRADIENT AND HOLE CONCENTRATION IN INEQUIVALENT CUO2 LAYERS OF TL2BA2CA2CU3O10-DELTA WITH DIFFERENT T-C

The (CU)-C-63 and O-17 NMR were measured in oriented ceramic samples o f Tl2Ba2Ca2Cu3O10-delta with various Tc values in the normal and super conducting states. The quadrupole coupling constants for copper and ox ygen from different CuO2 layers were obtained. The doping variation of the valence contribution to the electric field gradient at the Cu sit e was used for estimation of the hole concentration. In the overdoped T12223 sample with T-c(delta(1))<T-c(opt)(delta(opt)>delta(1)) the cha rge density in the inner layer (with four-fold oxygen coordination for Cu) differs from one in the outer plane (with five-fold oxygen coordi nation for Cu). Our results have shown that the inhomogeneity of the c harge distribution disappears in the underdoping regime.