Influence of nonuniform critical current density profile on magnetic   field behavior of AC susceptibility in 2D Josephson Junction Arrays
  Employing mutual-inductance measurements we study the magnetic field dependence of complex AC susceptibility of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays of unshunted Nb-AlO_x-Nb junctions. The observed behavior can be explained assuming single-plaquette approximation of the overdamped model with an inhomogeneous critical current distribution within a single junction. 
F.M. Araujo-Moreira, W. Maluf and S. Sergeenkov