Vortex motion in Nb/PdNi/Nb trilayers: new aspects in the flux flow state

TL;DR

This study investigates vortex line dynamics in Nb/PdNi/Nb heterostructures at microwave frequencies, revealing deviations from traditional models and new field-dependent behaviors in flux-flow resistivity.

Contribution

It provides new insights into flux-flow resistivity behavior in SFS heterostructures, especially regarding the influence of ferromagnetic layer thickness.

Findings

$ ho_{ff}$ deviates from Bardeen-Stephen model

$ ho_{ff}$ fits time-dependent Ginzburg-Landau at thin F layers

New field dependence observed for thicker F layers

Abstract

We study the dynamics of vortex lines in Supercondutor/Ferromagnet/Superconductor (SFS) heterostructures at microwave frequencies. We have employed swept-frequency, Corbino-disk and resonant, dielectric-resonator techniques to obtain the field and temperature dependence of the vortex-state parameters. We concentrate here on the genuine flux-flow resistivity $\rho_{ff}$, that we access at subcritical currents using a sufficiently high driving frequency. We find that $\rho_{ff}$ does not follow the well-known Bardeen-Stephen model. Instead, it is well described by a full time-dependent Ginzburg-Landau expression at very thin F layer thickness, but changes to a previously unreported field-dependence when the F layer exceeds a few nm.