  Skyrmions are topologically protected field configurations with particle-like
properties that play important roles in various fields of science. Recently,
skyrmions have been directly observed in chiral magnets. Here, we investigate
the effects of nonmagnetic impurities (structural point-like defects) on the
different initial states (random or helical states) and on the formation of the
skyrmion crystal in a discrete lattice. By using first-principle calculations
and Monte Carlo techniques, we have shown that even a small percentage of spin
vacancies present in the chiral magnetic thin film affects considerably the
skyrmion order. The main effects of impurities are somewhat similar to thermal
effects. The presence of these spin vacancies also induces the formation of
compact merons (bimerons) in both the helical and skyrmion states. We have also
investigated the effects of adjacent impurities producing only one hole (with
an almost circular shape) intentionally inserted into the plate (forming a
non-simply connected manifold) on the skyrmion crystal.
