Theoretical Investigation of Exchange Bias in Compensated Cases

The exchange bias (EB) of the ferromagnetic (FM)/antiferromagnetic (AFM) bilayers in a compensated case is studied by use of the many-body Green's function method of quantum statistical theory. The so-called compensated case is that there is no net magnetization on the AFM side of the interface. Our conclusion is that the EB in this case is primarily from the asymmetry of the interfacial exchange coupling strengths between the FM and the two sublattices of the AFM. The effects of the layer thickness, temperature and the interfacial coupling strength on the exchange bias HE are investigated. The dependence of HE on the FM layer thickness and temperature is qualitatively in agreement with experimental results. HE is nearly inversely proportional to FM thickness. When temperature varies, both HE and HC decrease with temperature increasing. The anisotropy of the FM layer only slightly influence HC, but does not influence HE