  We have found that some periods of interlayer exchange coupling (IEC)
oscillations as a function of cap-layer (CL) thickness may be suppressed if the
in-plane extremal spanning vectors of the cap- and ferromagnet-materials Fermi
surfaces do not coincide. The suppression of the IEC oscillations vs. the CL
thickness holds also if the magnetic slab thickness tends to infinity. On the
one hand, we have shown by means of very simple arguments that apart from the
well-known selection rules concerning the spacer- and cap-layers, another one
related with the magnetic sublayers has to be fulfilled in order that the
interlayer coupling oscillations $vs.$ CL thickness could survive. On the other
hand, the distribution of induced magnetic moments across the non-magnetic cap-
and spacer-sublayers have been computed and shown to reveal the underlying
periodicity of the materials they are made of (i.e. related to their bulk Fermi
surfaces) independently of whether or not the selection rules are fulfilled.
This means that the IEC oscillations are of global nature and depend on all the
sublayers the system consists of.
