We report on the effect of 0-5 monoatomic layers of Mn deposited at the interface of a CoFe/IrMn polycrystalline thin film. All samples were produced via sputtering. Thermal activation measurements were carried out using the well-established York Protocols. In conjunction with grain size analysis performed on each sample the value of the antiferromagnet (AF) anisotropy KAF was found. An increase in exchange bias Hex was found in the case of 1-2 atomic layers, however a sharp decrease was seen with the addition of further layers. There was no change in the median grain diameter DM , or in the median blocking temperature (TB ), and consequently KAF, with the addition of Mn. However in the samples with the Mn interfacial layers Hex was found to increase by up to 100 Oe when the setting field Hset, was varied from 5 to 20 kOe.