  An extreme type II superconductor with internal insulating regions, namely
cavities, is studied here. We find that the cavity-bearing superconductor has
lower energy than the defect-free superconductor above a critical magnetic
induction $B^*$ for insulating cavities but not for metallic ones. Using a
numerical approach for the Ginzburg-Landau theory we compute and compare free
energy densities for several cavity radii and at least for two cavity
densities, assuming a cubic lattice of spherical cavities.
