  We report on systematic ab-initio investigations of Co and Cr interlayers
embedded in Fe(001)/MgO/Fe(001) magnetic tunnel junctions, focusing on the
changes of the electronic structure and the transport properties with
interlayer thickness. The results of spin-dependent ballistic transport
calculations reveal options to specifically manipulate the tunnel
magnetoresistance ratio. The resistance area products and the tunnel
magnetoresistance ratios show a monotonous trend with distinct oscillations as
a function of the Cr thickness. These modulations are directly addressed and
interpreted by means of magnetic structures in the Cr films and by complex band
structure effects. The characteristics for embedded Co interlayers are
considerably influenced by interface resonances which are analyzed by the local
electronic structure.
