Dependence of exchange bias on structure of antiferromagnet in Fe/IrMn3

Single-crystal exchange biased multilayer thin-films consisting of an Fe layer on single-crystal chemically ordered L12-IrMn3 and disordered γ-IrMn3 were investigated using circularly and linearly polarised soft X-ray reflectivity to determine the interfacial magnetic structure between Fe and IrMn3. In ordered L12-IrMn3, we found that the Mn uncompensated moments at the interface are strongly pinned and only Fe rotational moments are observed. In disordered γ-IrMn3 the uncompensated moments are partially pinned, where the Mn moments are rotatable but the rotations are restricted. These findings are a crucial development in exchange bias theory to understand the force that drives the magnetic reversal process in ordered and disordered IrMn3.