Atomic Charge States in Tl2Ba2Can?1CunO2n+4 as Determined by the61Cu(61Ni),67Cu(67Zn) and133Ba(133Cs) Emission M�ssbauer Spectroscopy

Parameters of the electric field gradient tensors have been found for the Cu and Ba sites of the Tl 2 Ba 2 Ca n-1 Cu n O 2n+4 lattices by the 61 Cu( 61 Ni), 67 Cu( 67 Zn) and 133 Ba( 133 Cs) emission M6ssbauer spectroscopy. The same parameters have been calculated using the point charge approximation. An analysis of the obtained quantities has been carried out taking into consideration literature data on the 63 Cu nuclear quadrupole resonance. Agreement of the measured and calculated parameters could be reached assuming the holes resulting from lowering the valence of part of the Tl atoms to be placed mainly at oxygen sites of the Cu-O planes (especially, at oxygen sites of the Cu(2)-O planes for the Tl 2 Ba 2 Ca 2 Cu 3 O 10 compound).