The structure and interlayer exchange coupling in MBE-grown Fe/SiFe/Fe has been investigated. From structural analysis with LEED and from magnetic analysis with the magneto-optical Kerr effect, it is concluded that the Si spacer transforms into an ordered ${\mathrm{Si}}_{0.5}{\mathrm{Fe}}_{0.5}$ alloy. A strong antiferromagnetic coupling is found (maximum $-2.0\mathrm{}\mathrm{mJ}/{\mathrm{m}}^2$), the strength of which varies exponentially as a function of the spacer thickness. This behavior can be explained within the framework of recent coupling theories.

• Received 23 December 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.3023