Flux-flow induced giant magnetoresistance in all-amorphous superconductor-ferromagnet hybrids

TL;DR

This study investigates how flux flow of vortices in amorphous superconductor-ferromagnet hybrids causes giant magnetoresistance effects, revealing the influence of magnetic domain stray fields on superconducting vortex dynamics.

Contribution

It demonstrates flux-flow induced giant magnetoresistance in all-amorphous F/S heterostructures and highlights the role of magnetic domain stray fields in vortex behavior.

Findings

Large magnetoresistance peaks near coercive fields in trilayers

Stray magnetic fields from Bloch domains induce vortex flux flow

Bilayers show smaller effects due to domain wall alignment

Abstract

We present magnetoresistance measurements on all-amorphous ferromagnet (F) / superconductor (S) heterostructures. The F/S/F trilayers show large magnetoresistance peaks in a small field range around the coercive field of the F layers, at temperatures within and below the superconducting transition. This is interpreted as flux flow of weakly pinned vortices induced by the stray field of Bloch magnetic domains in the F layers. Bilayers show much smaller effects, implying that the Bloch walls of the F-layers in the trilayer line up and focus the stray fields. The data are used to discuss the expected minimum F-layer thickness needed to nucleate vortices.