  We have used spin-polarized neutron reflectometry to investigate the
magnetization profile of superlattices composed of ferromagnetic Gd and
superconducting Nb layers. We have observed a partial suppression of
ferromagnetic (F) order of Gd layers in [Gd($d_F$)/Nb(25nm)]$_{12}$
superlattices below the superconducting (S) transition of the Nb layers. The
amplitude of the suppression decreases with increasing $d_F$. By analyzing the
neutron spin asymmetry we conclude that the observed effect has an
electromagnetic origin - the proximity-coupled S layers screen out the external
magnetic field and thus suppress the F response of the Gd layers inside the
structure. Our investigation demonstrates the considerable influence of
electromagnetic effects on the magnetic properties of S/F systems.
