  Magneto-optical imaging studies on a high-quality Bi2Sr2CaCu2O8 single
crystal partially patterned with a triangular array of holes reveal enhanced
flux shielding in the patterned region of the sample. By mapping local magnetic
field and shielding current density distributions at different applied magnetic
fields and temperatures we determine the regime where pinning from the
patterned holes dominates over the intrinsic pinning in the sample. In this
regime, the flux density near the center of the patterned region is observed to
increase when the applied field is varied from below the matching field to just
above it, while significant magnetic field gradients are sustained in the
patterned region. Our measurements indicate heterogeneous pinning properties of
the vortex population, exhibiting signatures of both weak and strong pinning,
in the nanopatterned region of the superconductor.
