Vortex-Antivortex Pair Unbinding Driven by the Spin Texture of a Ferromagnet-Superconductor Bilayer

TL;DR

This paper investigates how the spin texture in a ferromagnet-superconductor bilayer influences vortex-antivortex pair dynamics, revealing magnetic field-dependent features linked to non-collinear magnetization and spin reorientation transitions.

Contribution

It provides new insights into the interplay between magnetic textures and vortex behavior in ferromagnet-superconductor bilayers, highlighting the role of spin reorientation transitions.

Findings

Dip in critical current density at specific magnetic fields

Peak in resistance correlating with vortex-antivortex dynamics

Normal component of magnetization assists in depairing vortex pairs

Abstract

We report the observation of a pronounced dip in the in-plane field (H//) dependence of the critical current density Jc(H) and a peak in resistance R(H) of a NbN-HoNi5 bilayer at temperatures below the magnetic ordering temperature (TCurie ~ 5.5 K) of HoNi5, which is lower than the onset temperature (~ 9 K) of superconductivity in the NbN layer. The extrema in Jc(H) and R(H) appear at fields much below the upper critical field of NbN. It is suggested that the origin of this feature is linked with the non-collinear magnetization of HoNi5 whose normal component assists in depairing of Pearl vortex-antivortex pairs in the system. A spin reorientation transition driven by the H// diminishes this normal component and consequently the excess dissipation.