Interlayer exchange coupling in Fe/SiFe/Fe sandwiches

The interlayer exchange coupling in Fe/c-FeSi/Fe has been theoretically investigated in the framework of the ab initio tight-binding linear-muffin-tin-orbitals method. The system is modeled according to recent structural analysis performed with LEED techniques, which show that the Si spacer transforms into an ordered Si0.5Fe0.5 alloy in the CsCl structure (c-FeSi). We obtain antiferromagnetic coupling between the Fe layers for spacer thicknesses smaller than about 17 Å with non-monotonous decaying behavior. The density of states of the FeSi spacer at the Fermi level is very small, and displays a sharp peak at about 0.5 eV above the Fermi level. Our results are discussed and compared with available experimental data.