Influence of magnetism on superconductivity in epitaxial Fe/Nb bilayer systems

We studied the superconductivity of molecular-beam-epitaxy-grown epitaxial Nb(110) thin films covered by Fe(110) monocrystalline layers with thicknesses ${d}_{\mathrm{Fe}}$ between 4 and 30 \AA{}. We find a nonmonotonous dependence of the superconducting transition temperature ${T}_{c}$ on ${d}_{\mathrm{Fe}},$ however, without a maximum in ${T}_{c}{(d}_{\mathrm{Fe}})$ as observed earlier in Nb/Fe layers prepared by sputtering techniques. We argue that the change in the ${T}_{c}{(d}_{\mathrm{Fe}})$ curve is caused by a smaller thickness of the nonmagnetic Fe-rich interlayer at the Nb/Fe interface and can be explained within the same model developed previously for the explanation of the maximum in ${T}_{c}{(d}_{\mathrm{Fe}})$ in sputtered Nb/Fe layers.