Superfluid Density and Vortex Dynamics in S/F/S Heterostructures

We present electrical transport measurements in the microwave range in Superconductor/Ferromagnet/ Superconductor Nb/Pd0.84 Ni0.16 /Nb heterostructures, with different thickness of the ferromagnetic layer. We employ a wideband (1–20 GHz) Corbino disk technique to obtain the real part of the microwave resistivity in the vortex state. We focus on the fundamental properties that can be derived from measurements of the pinning property of the vortices. In particular, we estimate the superfluid density at the same reduced temperature. We describe the method to derive from the measurements the pinning constant kp, and to estimate the the superfluid density. We find a strong reduction of the superfluid density with the ferromagnetic layer thick- ness. Finally, we compare our results to zero-temperature superfluid density estimated in bilayers.