Ab initio study of electric transport and interlayer exchange coupling in Fe-Si-Fe systems

We present a first principles study of the magnetoresistance (MR) perpendicular to the planes of atoms and the interlayer exchange coupling (IEC) in Fe-Si-Fe trilayers. In both cases the dependence on the number of spacer layers is investigated, whereby the spacer thickness ranges between 3 and 21 Angstrom for the IEC and extends to 33 Angstrom for the MR in order to obtain the asymptotic behavior. Additionally, the influence of alloy formation at the interfaces on the MR and the IEC is examined. The calculations of the electronic structure are performed within the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method and the transport properties are derived from the Kubo-Greenwood equation. Our results give evidence that interdiffusion is one of the origins of the small MR, which is observed experimentally in Fe/Si/Fe trilayers. AFM coupling occurs for spacers thicker than 4 Angstrom which is in accordance with the experimental findings. It seems that interdiffusion stabilizes AFM coupling in Fe-Si-Fe trilayers.