Antiferromagnetic interlayer coupling through a thin MgO layer in γ-Fe2O3/MgO/Fe(001) multilayers

We investigated the magnetization process of epitaxial MgO(001)/gamma-Fe2O3/MgO/Fe(001) multilayers. When the thickness of a MgO spacer layer was less than 1.0 nm, an antiferromagnetic interlayer exchange coupling (IEC) between Fe(001) and gamma-Fe2O3(001) layers appeared. Unlike the oscillatory IEC in metallic systems, the sign of the observed IEC is only antiferromagnetic. The strongest coupling constant was found to be around -1.8 erg/cm(2) at the MgO thickness of 0.5 nm. This antiferromagnetic coupling via the insulating MgO layer is possibly understood within the framework of spin polarized tunneling models.