Critical current vs. magnetic field dependence in ramp-zigzag Josephson junctions

We study the critical current I_c dependence on applied magnetic field H for multifacet YBa_2Cu_3O_{7-\delta}-Au-Nb zigzag Josephson junctions. For many experiments one would like to apply a homogeneous field parallel to the junction plane. However, even tiny misalignments can cause drastic deviations from homogeneity. We show this explicitly by measuring and analyzing I_c vs. H for an 8 facet junction, forming an array of 4\times(0-\pi)-segments. The facet width is 10\mu m. H is applied under different angles \theta relative to the substrate plane and different angles \phi relative to the in-plane orientation of the zigzags. We find that even a small misalignment \theta \sim 0.2^\circ can cause a substantial inhomogeneity of the flux density inside the junction, drastically altering its I_c vs. H interference pattern. We also show, that there is a dead angle \theta_d of similar magnitude, where the average flux density completely vanishes.