We study the critical current $I_c$ dependence on applied magnetic field $H$ for multifacet ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$/Au/Nb ramp-type zigzag Josephson junctions. For many experiments, one would like to apply a homogeneous field in the junction plane. However, even tiny misalignments can cause drastic deviations from homogeneity. We show this explicitly by measuring and analyzing $I_c$ versus $H$ for an eight-facet junction, forming an array of $4\times (0-\pi )$ segments. The ramp angle is ${\theta }_r=8^{\circ }$. $H$ 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 a homogeneous flux distribution is only achieved for an angle ${\theta }_h\approx 1^{\circ }–2^{\circ }$ and that even a small misalignment $\sim$0.1${}^{\circ }$ relative to ${\theta }_h$ can cause a substantial inhomogeneity of the flux density inside the junction, drastically altering its $I_c$ versus $H$ interference pattern. We also show that there is a dead angle ${\theta }_d^{*}$ relative to ${\theta }_h$ of similar magnitude, where the average flux density completely vanishes.

• Received 1 August 2012

DOI:https://doi.org/10.1103/PhysRevB.86.144531