THE FREQUENCY AND DC MAGNETIC-FIELD DEPENDENCE OF THE RF PENETRATION DEPTH IN THE SOLID AND FLUID VORTEX PHASES OF BI-PB-SR-CA-CU-O

The frequency and DC magnetic field dependence of the change in the RF penetration depth resulting from vortex-induced dissipation has been measured in Bi-Pb-Sr-Ca-Cu-O above and below the depinning transition. The dissipation is shown to have a linear dependence on B1/2 at const ant temperature in the solid and fluid vortex phases with a different slope in each phase. The dissipation is observed to be independent of frequency in the pinned regime but decreases with increasing frequency in the fluid state. The magnetic field at which the transition occurs at constant temperature is frequency dependent, decreasing with incre asing frequency. The results are in general agreement with theoretical predictions of the magnetic field and frequency dependence of the pen etration depth.