Exchange bias of patterned NiFe/IrMn film

Exchange bias of different types of patterned NiFe/IrMn microstructures have been studied using the magneto-optical Kerr effect. In general, the exchange field was found to decrease when the exchange coupled double layers were patterned into small dimensions. The magnitude of decrease, however, depends on whether only the NiFe film was patterned or both the NiFe and IrMn were patterned, and also in the cases of grating patterns, whether the grating is along the exchange bias direction or perpendicular to it. The fact that the largest decrease has been found in samples in which both the NiFe and IrMn have been patterned into small square shape of dots suggests that the domain structures in the antiferromagnetic layer mainly determine the strength of exchange bias field.