Size effect on current transport properties in the mixed state of YBCO thin film

Abstract We have investigated the influence of sample width on the transport properties in YBCO thin film using 10, 120, and 1200 μm-wide bridges formed in a same c -axis oriented YBCO film deposited on a SrTiO 3 substrate. We measured I–V characteristics of the bridges at various temperature, T , and magnetic field, B , perpendicular to the film surface. It has been found that the so called glass–liquid transition field, B GL , reduces as the sample width becomes narrower, while the critical temperature, T c , and critical current density, J c , in the glass region ( B B GL ) are almost independent of the width of the bridges. The good agreement of T c and J c in three bridges indicates high uniformity of the bridges and that the reduction of B GL does not come from the degradation of the film. The measured width dependence of B GL can be scaled with a constant critical index as can be predicted by the percolation model at all measured temperature region from 70 to 85 K. The influence of sample width on J c has also been discussed based on the scaling analysis.