Exchange bias in nanoscale antidot arrays

Exchange bias effects have been systematically investigated in nanoscale Cu (10 nm)/Ni80Fe20 (30 nm)/Ir75Mn25 (30 nm)/Cu (2 nm) multilayer antidot arrays. The antidot arrays exhibit asymmetric and shifted hysteresis loops along the induced exchange bias direction, with higher coercivity and exchange bias field values as compared to a continuous film deposited under identical conditions. The evolution in exchange bias field with increasing antidot diameter is ascribed to the constraints imposed on the domain size in the Ir75Mn25 layer and reduced ferromagnetic-ferromagnetic interactions in the Ni80Fe20 layer.