Magnetic field dependence of the critical current in polycrystalline YBCO bridges with decreasing width

We have performed a theoretical approach of the magnetic field dependence o f the critical current, I-c(B) (B = 0-35 Oe), for superconducting samples w ith different sizes and critical current densities. In order to check our m odel we have adjusted a systematic experimental study made on variable widt h bridges (w = 50-2000 mu m) enmaved in YBCO thick films. Regarding our bri dges as sets of random linear arrays of coupled Josephson junctions, and wi th some microstructural knowledge, we have obtained families of curves I-c( B, w) that reproduce in a semi-quantitative manner the observed experimenta l results. The percolative behavior and quantum interference effects betwee n different current paths were considered to model qualitatively the experi mentally observed quasi-oscillatory I-c(B) dependencies. The mismatch betwe en our model and others' similar attempts is also discussed. (C) 1999 Publi shed by Elsevier Science B.V. All rights reserved.