MAGNETORESISTIVITY NEAR THE SUPERCONDUCTING TRANSITION OF HIGH-TEMPERATURE COPPER-OXIDE SUPERCONDUCTORS WITH NONUNIFORMLY DISTRIBUTED T-C INHOMOGENEITIES

We have measured the in-plane magnetoresistivity, rho(T,H), of YBa2Cu3 O7-delta, Bi2Sr2CaCu2O8 and Tl2Ba2Ca2Cu3O10 crystals with small stoich iometric inhomogeneities at long length scales and uniformly and non-u niformly distributed in the crystals. These stoichiometric inhomogenei ties (mainly of the oxygen content) lead to T-c inhomogeneities, which deform the rho(T,H) curves mainly near T-c. In the case of non-unifor mly distributed inhomogeneities, sharp rho(T,H) peaks may also appear, very sensitive to the applied magnetic field. This leads to a very an isotropic and negative magnetoresistivity. We will show that these dif ferent effects may be explained at a quantitative level in terms of te mperature dependent electrical current redistributions. (C) 1997 Publi shed by Elsevier Science Ltd.