  We numerically and experimentally investigate the influence of single defects
consisting of a missing antidot on the spin configurations in rectangular
permalloy antidot lattices. The introduction of such lattice defects leads to
the nucleation of complex domain structures after the decay of a saturating
magnetic field. Micromagnetic simulations yield four typical domain
configurations around the defect having distinct energy densities. The
existence of the four spin configurations is confirmed by magnetic force
microscopy on antidot lattices containing individual defects.
