Double percolation effects and fractal behavior in magnetic/superconducting hybrids

TL;DR

This paper investigates how labyrinth domain structures in magnetic/superconducting bilayers influence superconductivity nucleation and percolation, revealing a double percolation effect and fractal behavior affecting the upper critical field.

Contribution

It demonstrates the tunability of superconductivity nucleation on a fractal network via magnetic history and reveals a double percolation process involving domain arrangement and fractal cluster growth.

Findings

Superconductivity nucleation depends on magnetic domain configuration.

The upper critical field exhibits behavior characteristic of fractal networks.

Double percolation effects are observed in FM/SC bilayers.

Abstract

Perpendicular magnetic anisotropy ferromagnetic/ superconducting (FM/SC) bilayers with a labyrinth domain structure are used to study nucleation of superconductivity on a fractal network, tunable through magnetic history. As clusters of reversed domains appear in the FM layer, the SC film shows a percolative behavior that depends on two independent processes: the arrangement of initial reversed domains and the fractal geometry of expanding clusters. For a full labyrinth structure, the behavior of the upper critical field is typical of confined superconductivity on a fractal network.