Antiferromagnetic interlayer coupling in FeÕc-SiFeÕFe sandwiches and multilayers

We report an ab initio study of the interlayer exchange coupling in Fe/c-FeSi/Fe sandwiches and Fe/c-FeSi multilayers. We perform several structural studies, which show the stability of the CsCl arrangement seen experimentally for the spacer. We study the effect of pinholes, interface roughness, or structural misconfigurations of the spacer on the sign and magnitude of the exchange constant J. We have extended Bruno’s theory to account for the effect of different effective masses on the exchange constant, leading to an excellent description of its asymptotic behavior, as compared with experiments. The results presented here allow us to identify Fe/c-FeSi sandwiches as an example of a new class of magnetic multilayer devices, where the spacer material is semimetallic.