Transport and magnetic measurements on Bi2+xCa1-xSr2Cu2O8+δ

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Abstract
The authors have measured the susceptibility, magnetisation, resistivity, thermopower and Hall coefficient for a number of samples of the recently discovered superconductor of nominal composition Bi2+xCa1-xSr2Cu2O8+ delta . They find that sintered ceramic pellets show a small volume fraction superconducting at 110 K and a further transition with onset at 85 K to a zero resistance state at 70 K. The Meissner effect shows 13% by volume flux exclusion at 20 K. In the normal state, they find a temperature-independent magnetic susceptibility of about 2.8*10-4 emu/(mol Cu); this value is relatively insensitive to variations between batches. In contrast, both the thermopower and Hall coefficient show a wide spread in behaviour, both p- and n-type, and this they attribute to the presence of other metallic phases in addition to the superconducting phases.