  Magnetic nanostructures revealing exchange bias effect have gained a lot of
interest in recent years due to their possible applications in modern devices
with various functionalities. In this paper, we present our studies on
patterned [CoO/Co/Pd]10 multilayer where ferromagnetic material is in a form of
clusters, instead of being a continuous layer. The system was patterned using
nanosphere lithography technique which resulted in creation of an assembly of
well-ordered antidots or islands over a large substrate area. We found that the
overall hysteresis loop of the films consists of hard and soft components. The
hard component hysteresis loop exhibits a large exchange bias field up to -11
kOe. The patterning process causes a slight increase of the exchange field as
the antidot radius rises. We also found that the material on edges of the
structures gives rise to a soft unbiased magnetization component.
