Transition from strong to weak coupling  regime with lowering T_c in Tl₂Ba₂CuO_6+x.

  Abstract:
Using  ²⁰⁵Tl NMR, the changes in electronic properties in the normal and superconducting state of the Tl₂Ba₂CuO_6+x   compound associated with variation of T_c, are studied  in samples with T_c=30, 100, and 115K. Decreasing T_c with oxygen doping is shown to be associated with the growth of the static electron spin susceptibility and with lowering the  D/T_c ratio (D is superconducting gap). This effect indicates to the corresponding weakening of coupling regime.