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-xCux. Dilution by Cu atoms throughout the volume of the AFM IrMn gives rise to an enhanced EB field (HEB) for 5 K<or=T<or=350 K. The thermoremanent magnetization of the sole AFM layer is also enhanced with dilution, shows qualitatively the same temperature dependence as HEB, 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.