Superconducting/ferromagnetic proximity effect mediated by Cr spacer layers

Abstract

We have studied the superconducting proximity effect in the thin film system Fe/Cr/V/Cr/Fe where the Cr layers play the role of screening layers between the superconducting V-layer and the strongly pair breaking Fe-layers. When keeping the thickness of the Fe-layers dFe fixed and varying the thickness of the Cr-layers dCr, the superconducting transition temperature Tc first rises reaching a maximum at dCr=40 Å and then sharply drops for larger Cr-thickness. Keeping dCr constant and varying dFe the superconducting transition temperature becomes independent on dFe for dCr>40 Å. The results demonstrate that the Cooper pairs penetrate into the Cr-layer to a depth of about 40 Å. From our experimental results we suggest that the Cr-layer is nonmagnetic for dCr<40 Å and undergoes a transition to an incommensurate spin density wave state for dCr>40 Å.