Antiferromagnetic interlayer exchange coupling between Fe3 O4 layers across a nonmagnetic MgO dielectric layer

We have investigated the interlayer exchange coupling between the epitaxial spinel Fe3 O4 layers across an insulating nonmagnetic MgO spacer. The epitaxial structure used for these investigations was Fe3 O4 (10 nm) MgO (0.8-3 nm) Fe3 O4 (10 nm) NiO (15 nm) multilayers grown on MgO (100) substrates. We find that the two Fe3 O4 layers are antiferromagnetic coupled through the MgO spacer when the MgO thickness is less than 1.5 nm. Furthermore, ab initio calculation of IEC for FeMgOFe indicates the importance of electrode states, in particular, partial oxidation of the ferromagnetic electrodes.