Anisotropy dominated radio frequency vortex dynamics in Bi2Sr2CaCu2O8 thick film on silver tapes

Vortex dynamics at radio frequency Cn is studied in flexible tape samples o f Bi2Sr2CaCu2O8 superconductor as functions of de magnetic field, temperatu re and orientation between the field and plane of the tape. The rf response in the geometry when the de field is perpendicular to the tape suggests tw o distinct regimes of vortex dynamics, one corresponding to a moderately pi nned three-dimensional vortex solid and the other a liquid of two-dimension al vortices. The rf penetration depth in the 3D pinned phase is analyzed in the framework of the theories of single vortex pinning and the behaviour o f pinning force constant k(p) is discussed. In the vortex solid phase we se e evidence of flux lock-in between the CuO2 planes. The angle dependent res ponse in the liquid shire scales with the component of de field parallel to c-axis. The scaling analysis shows some renormalization of the anisotropy due to non-zero deviations from a perfect alignment of the grains parallel to the plane of the tape. (C) 1999 Elsevier Science B.V. All rights reserve d.