  We demonstrate a 20-fold enhancement in the strength of the RKKY interlayer
exchange in dilute-ferromagnet/normal-metal multilayers by incorporating
ultrathin Fe layers at the interfaces. Additionally, the resulting increase in
the interface magnetic polarization profoundly affects the finite-size effects,
sharpening the Curie transition of the multilayer, while allowing to separately
tune its Curie temperature via intralayer magnetic dilution. These results
should be useful for designing functional materials for applications in
magneto-caloric micro-refrigeration and thermally-assisted spin-electronics.
