Antiferromagnetic interlayer exchange coupling across epitaxial, Ge-containing spacers

We give experimental evidence of antiferromagnetic interlayer exchange coupling of Fe(001) layers across epitaxial, Ge-containing spacers consisting of either Ge wedges embedded between two Si boundary layers or Si-Ge-multilayers. The coupling strengths are of the order of 1 mJ/m(2) and decay on a length scale below 2 Angstrom as determined from magneto-optic Kerr effect and Brillouin light scattering. The coupling evolves with the spacer thickness from ferromagnetic to prevailing 90degrees or antiferromagnetic for Ge wedges and Si-Ge multilayers, respectively. The bilinear coupling is comparable in both cases, but the biquadratic contribution is suppressed for Si-Ge-multilayer spacers. Thus, Si-Ge-multilayer spacers give rise to perfect antiparallel alignment of the Fe film magnetizations. (C) 2003 American Institute of Physics