Vibrating reed studies on high-Tc superconductors

Vibrating reed (VR) measurements on single crystal and ceramic 1-2-3 and melt-processed polycrystalline Bi-based compounds in a wide range of temperature (4.2-100 K) and magnetic field (B=0-4 T) are presented. The depinning line (DL) determined by the VR technique is equivalent to the irreversibility line determined by magnetization and susceptibility measurements. A comparison of the results on single crystal and polycrystalline 1-2-3 compounds indicates that the VR technique is sensitive to the intrangular properties of the polycrystalline reed. It is found that the DL for 1-2-3 compounds is much steeper than that for Bi-based compounds, reflecting an intrisically different pinning in both the materials, in agreement with the measured elastic coupling (Labusch constant α(B,T)). (author). 20 refs