Interlayer Magnetic Coupling in Magnetic/Kondo Lattice Multilayered Structures

We study the interlayer coupling between metallic ferromagnetic materials, separated by a thin insulator spacer, modelled as a Kondo insulator, in an attempt to understand the behavior of Fe/FeSi multilayered structures. We find that interlayer magnetic coupling is antiferromagnetic at large band filling and ferromagnetic at small band filling with only one change in sign as a function of electron density. This dependence of the coupling on the electron density is contrasted with the pure RKKY coupling that would arise in a simple metal. It gives a way of understanding the photoinduced antiferromagnetic interlayer coupling in Fe/FeSi superlattices seen in recent experiments.