Superfluid density of superconductor-ferromagnet bilayers

Abstract

We report the first measurements of the effective superfluid density n_S(T) \propto λ^{-2}(T) of Superconductor-Ferromagnet (SC/FM) bilayers, where λis the effective magnetic field penetration depth. Thin Nb/Ni bilayers were sputtered in ultrahigh vacuum in quick succession onto oxidized Si substrates. Nb layers are 102 A thick for all samples, while Ni thicknesses vary from 0 to 100 A. T_C determined from λ^{-2}(T) decreases rapidly as Ni thickness d_Ni increases from zero to 15 A, then it has a shallow minimum at d_Ni \approx 25 A. λ^{-2}(0) behaves similarly, but has a minimum several times deeper. In fact, λ^{-2}(0) continues to increase with increasing Ni thickness long after T_C has stopped changing. We argue that this indicates a substantial superfluid density inside the ferromagnetic Ni films.

13 pages, 2 figures, MMM 2007 proceedings

References in corpus (4)

• Proximity effects in superconductor-ferromagnet heterostructures
• Coupling of two superconductors through a ferromagnet : evidence for a pi-junction
• Nonmonotonic critical temperature in superconductor/ferromagnet bilayers
• Quantitative analysis of proximity effect in $Nb/C{o}_{60}F{e}_{40}$, Nb/Ni, and $Nb/C{u}_{40}N{i}_{60}$ bilayers

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