Strong coupled superconductor in proximity with a quench-condensed ferromagnetic Ni film: A search for oscillating Tc

Abstract

We present results of in situ transport and tunneling measurements on a quench-condensed (QC) Pb film covered by a QC ferromagnetic Ni layer. This experiment provides new evidence in the controversy over the existence of inhomogeneous superconductivity in a superconducting/ferromagnet (S/F) system. The critical temperature of the superconducting Pb/Ni bilayer has been measured for numerous thicknesses of Pb ranging from 5 to 80 nm. No oscillatory behavior as a function of Ni thickness has been observed in the variation of Tc, implying no π state in those bilayers. These results are interpreted in light of recent theoretical developments. Tunneling measurements of (dI/dV) on Pb/Ni also show a monotonic depairing effect in the density of states of Pb versus the Ni thickness, which further confirms the absence of nonconventional superconductivity in this Pb/Ni system.

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