THE INFLUENCE OF THE STRUCTURE ON THE ELECTRICAL AND MAGNETIC-PROPERTIES OF BI2SR2CACU2O8-CRYSTALS(DELTA SINGLE)

The correlation between the structure, chemical composition, electrica l and magnetic properties of Bi2Sr2CaCu2O8+delta single crystals is pr esented. As revealed by SEM measurements, the small samples (approxima tely 1 mm x 1 mm x 0.2 mm) are stacks of thin plates (1-2 mu m). Micro compositional measurements (energy dispersive spectroscopy) show the B i2Sr2CaCu2O8+delta (2212)-phase and a small quantity of residual phase s enriched in bismuth and strontium and calcium-deficient. Magneticall y modulated microwave absorption measurements (MAMMA) lead to a value for the anisotropy of the upper critical field of about 7, which is mo re than twice the reported value for YBa2Cu3O7-delta single crystals ( also determined from MAMMA responses). The plot of the resistance vers us temperature suggests that only the first 10-20 plates from the surf ace of the sample have a contribution to the sample conductivity. The imaginary part, chi'', of the magnetic susceptibility of our samples s hows three peaks.