Flux distributions of an artificially granular YBa2Cu3O7-delta thin film observed using magneto-optic imaging

Flux distributions in a YBa2Cu3O7-delta thin film with artificial granulari ty are observed by means of magneto-optic imaging. At low magnification, fl ux patterns generated exclusively by the intergranular currents flowing in the intergranular area ("effective medium'') are directly observed. The pro perties of this effective medium are studied by taking flux density profile s that reveal the intergranular current density. As the observations at hig h magnifications show the flux penetration and pinning within the individua l disks, we can identify and study the different contributions of the inter granular and intragranular current densities to the flux patterns. We show that our model sample reproduces several features observed, e.g,, in Ag-she athed (Pb,Bi)(2)Sr2Ca2Cu3O10-delta.B tapes. (C) 2000 Elsevier Science B.V. All rights reserved.