I-V characteristics of grain boundaries in Sm1Ba2Cu3O7-δ thin films

Abstract

The transport properties of Sm1Ba2Cu3O7-delta films, which were grown on the bi-crystalline SrTiO3 substrates of 24degrees, 30degrees, 36.8degrees and 45degrees misorientation angles, were investigated by the measurements of the I-V curves at 77 K under various magnetic fields. When the voltages were high enough, the I-V curves became straight. The resistances estimated from the slopes were almost independent of the applied fields mostly for the high-quality films. For the slightly low-quality films, the zero field resistances were smaller than those for other fields. When the voltages were low enough, the relations between voltages and currents approximately satisfied the power law. The exponents increased by one order of magnitude as the field was changed from 0 to I T. The field dependences of the critical current densities varied according to the voltage of the criterion. The misorientation angle dependence of the critical current density was weaker than that of the Y1Ba2Cu3O7-delta grain boundaries. (C) 2003 Published by Elsevier Science B.V.