  By employing mutual-inductance technique and using a high-sensitive bridge,
we have thoroughly investigated (both experimentally and theoretically) the
temperature and magnetic field dependence of complex AC susceptibility of
artificially prepared highly ordered (periodic) two-dimensional Josephson
junction arrays (2D-JJA) of both shunted and unshunted Nb-based tunnel
junctions as well as disordered three-dimensional arrays (3D-JJA). This paper
reviews some of our latest results regarding the influence of non-uniform
critical current density profile on magnetic field behavior of AC
susceptibility in 2D-JJA, and the origin of remanent magnetization in
disordered 3D-JJAs.
