Vibrating-reed studies on non-single-phase Bi-Ca-Sr-Cu-O superconducting ceramics

The resonance frequency $\ensuremath{\omega}$ and damping $\ensuremath{\Gamma}$ of two selected reeds of Bi-Ca-Sr-Cu-O ceramics were measured between 4.2 and 100 K in different applied magnetic fields up to 0.3 T. The samples showed large anomalies in $\ensuremath{\omega}$ and $\ensuremath{\Gamma}$ at \ensuremath{\simeq}60 and \ensuremath{\simeq}45 K indicating the existence of different superconducting phases. These anomalies can be interpreted in terms of pinning and hysteretic motion of flux lines. Within experimental resolution x-ray-powder patterns resemble that of the 85-K superconductor ${\mathrm{Bi}}_{2}$Ca${\mathrm{Sr}}_{2}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8}$.

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