Apparent strong biquadratic contributions to the interlayer exchange coupling in Fe/Si multilayers

We have studied the interlayer exchange coupling in sputtered Fe/Si multilayers both by integrating and by depth-sensitive magnetic methods. We find that the degrees of antiferromagnetic alignment of adjacent ferromagnetic layers and their rotation process in an applied magnetic field depend on the position in the multilayer stack. The observed vertical and lateral variations of the coupling properties are able to mimic an apparent strong biquadratic coupling.