EFFECTIVE PINNING POTENTIAL IN EPITAXIAL YBa 2 Cu 3 O 7-δ THIN FILM

The temperature dependence of the resistivity of an epitaxial YBa 2 Cu 3 O 7-δ thin film has been measured in various magnetic fields up to 7T applied parallel to the c-axis near T c . The result shows that the resistivity below T c can be well fitted by thermally activation flux motion. The current density dependence of the effective pinning potential follows a logarithmic law proposed by Zeldov et al. The temperature and magnetic field dependence of the effective pinning potential follows U(H,T)=U 0 (1-T/T c )H -α , with α=0.63, showing 2D behavior, It is consistent with the plastic deformation model of the flux-line lattice at flux-line-lattice dislocations.