Dc vortex-flow resistivity in an epitaxially grown MgB2 film probed by pulsed current measurements

Abstract

Abstract Using pulsed currents, we measure the dc vortex-flow resistivity ρf in a fast-flow regime for an epitaxially grown MgB2 film. In the vortex-solid phase the current-voltage (I-V) characteristics in different magnetic fields B exhibit a crossover from nonlinear to linear behavior with an increase in I, indicating a change from pinning-dominated to viscous-force dominated flow. ρf (B) extracted from the slope of the linear part of the I − V data shows an unusual field dependence with strong enhancement at low B similar to that reported from microwave surface impedance. The results suggest that two-band properties can be also detected by dc measurements with pulsed currents in MgB2 films.