Effects of cu dilution in IrMn on the exchange bias of CoFe/IrMn bilayers

The effect of nonmagnetic dilution in metallic antiferromagnets (AFMs) on the exchange bias (EB) has been investigated from a structural, magnetic, and Monte Carlo simulation point of view in bilayers of CoFe/(IrMn)(1-x)Cu-x. Dilution by Cu atoms throughout the volume of the AFM IrMn gives rise to an enhanced EB field (H-EB) for 5 K <= T <= 350 K. The thermoremanent magnetization of the sole AFM layer is also enhanced with dilution, shows qualitatively the same temperature dependence as H-EB, and is at the origin of the EB mechanism. Monte Carlo simulations based on a Heisenberg model and temperature dependent uncompensated AFM moments confirm well the experimental results.