CU-67(ZN-67) MOSSBAUER EMISSION-SPECTROSCOPY OF TL2BA2CUO6 AND TL2BA2CACU2O8

The parameters of the crystal electric-field gradient at the copper si tes of Tl2Ba2CuO6 and Tl2Ba2CaCu2O8 have been determined by Mossbauer emission spectroscopy using the Cu-67(Zn-67) isotope, and calculated i n the point-charge approximation. The results obtained are analyzed us ing the available Cu-63 nuclear quadrupole resonance data. The experim ental and calculated data can be brought in agreement if one assumes t hat the holes appearing after part of the thallium atoms lower their v alency become localized primarily at the oxygen sites lying in the pla ne of the copper ions. (C) 1997 American Institute of Physics.