Current-density dependence of the vortex pinning energy in YBaCuO

Abstract

Measurements of the electrical resistivity, using pulsed currents of various magnitudes, in the mixed state of YBaCuO microbridges are reported. The onset of resistance follows a thermally activated behaviour of flux line motion. The dependence of the pinning potential barrier U on the current density j was investigated, revealing two distinctly different regions. At moderate current densities j < 10 4 A/cm 2, no change of U upon current density was observed. We associate this behaviour with thermally assisted flux flow. At high current densities, U declines logarithmically, in accordance with the flux creep picture and a particular pinning potential well proposed by Zeldov et al.