POWER-LAW DISSIPATION, COLLECTIVE PINNING, AND GRANULARITY IN TLBACACUO THIN-FILMS

Abstract

The influences of the applied magnetic field and temperature on flux dynamics have been investigated in dc-sputtered high-T-c Tl-Ba-Ca-Cu-O thin films. It was found that the current-voltage characteristics can be fitted by an empirical power-law equation over a wide range of dissipation. It then allowed us to easily derive an exponent showing a strong dependence on the magnetic field at lower field regime (< 400 Oe). The exponent, on the other hand, showed a relatively weaker dependence os temperature. The physical implications of the temperature and field dependiencies of the power-law exponent were discussed within the frameworks of collective pinning model. Evidences for collective pinning effects induced by the intergranular weak-link networks were further demonstrated to lend strong support to the present conjecture on the flux dynamics in these films.