MAGNETORESISTANCE AND CONDUCTIVITY FLUCTUATIONS IN SINGLE CRYSTALLINE BI1.7PB0.3SR1.9CACU1.9O8+X

The magnetoresistance of a Bi1.7Pb0.3Sr1.9CaCu1.9O8+x single crystal with T(c) = 91.5 K has been investigated in pulsed magnetic fields up to 22 T and in the temperature range T = (67-100)K. The experimental data at T< T(c) are scaled with the Larkin two-dimensional fluctuation expression. It is shown that the resistive transition widening in a magnetic field, which suppresses the phase coherence between the superconducting CuO2 planes, enables one to treat these planes as independent two-dimensional superconducting sheets with giant conductivity fluctuations. The magnetoresistance and excess conductivity above T(c) are analysed in the framework of the Aslamazov-Larkin model.