Magneto-optic imaging of flux penetration into an artificially granular high-Tc superconductor

A YBa2Cu3O7- (YBCO) thin film is patterned into a hexagonal close packed lattice of disks which are touching each other at the circumferences in order to enable the flow of an intergranular current. Such a sample was suggested by Koblischka et al. [Appl. Phys. Lett 70, 514 (1997)] as a model for a layered granular structure like in a Bi2Sr2Ca2Cu3O10- tape. Magnetization measurements reveal an anomalous position of the low field peak (central peak) similar to the tapes. Magneto-optic imaging is employed to visualize the local field distributions