  A graded distribution of pinning centers (antidots) in superconducting MoGe
thin films has been investigated by magnetization and magneto-optical imaging.
The pinning landscape has maximum density at the border, decreasing
progressively towards the center. At high temperatures and low fields, where
this landscape mimics the vortex distribution predicted by the Bean model, an
increase of the critical current is observed. At low temperatures and fields,
the superconducting performance of the non-uniform sample is also improved due
to suppression of thermomagnetic avalanches. These findings emphasize the
relevance of non-uniform pinning landscapes, so far experimentally unexplored,
on the enhancement of pinning efficiency.
