TRANSITION FROM STRONG TO WEAK-COUPLING WITH DECREASING TC IN THE TL2BA2CUO6+X SYSTEM

The effect of an increase in the oxygen content on the parameters of t he electronic system in the normal and superconducting states has been studied in oriented samples of the high-T(c). system Tl2Ba2CuO6+x wit h T(c)'s from 115 to 30 K (with x from 0 to 0.3). The study was carrie d out by an NMR method using Tl-205. The superconducting gap is found from the temperature dependence of the rate of spin-lattice relaxation and from the Knight shift of Tl-205. The ratio DELTA/T(c) decreases w ith decreasing T(c). This behavior indicates a corresponding weakening of the coupling upon doping with oxygen.