CU-61(NI-61) AND BA-133(CS-133) MOSSBAUER EMISSION-SPECTROSCOPY OF TL2BA2CAN-1CUNO2N+4

The parameters of the electric-field gradient tensor at copper and bar ium sites in the Tl2Ba2Can-1CunO2n+4 (n=1,2,3) lattice have been deter mined by Cu-61(Ni-61) and Ba-133(Cs-133) Mossbauer emission spectrosco py, and calculated in the point-charge approximation. The calculated p arameters can be reconciled with experiment if one assumes that the ho les produced as the valence state of a part of thallium atoms is lower ed are localized predominantly on the oxygen sublattice lying in the s ame plane with copper atoms [in the Cu(2) plane in the Tl2Ba2Ca2Cu3O10 lattice]. Ba-133(Cs-133) Mossbauer emission spectroscopy data agree q ualitatively with the proposed models of charge distribution in the Tl 2Ba2Can-1CunO2n+4 lattices. (C) 1998 American Institute of Physics.