Magnetic proximity effect in Nb/Gd superlattices seen by neutron reflectometry

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(dF)/Nb(25 nm)]12 superlattices below the superconducting (S) transition of the Nb layers. The amplitude of the suppression decreases with increasing dF. 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. © 2019 American Physical Society