Controlling supercurrents and their spatial distribution in ferromagnets

TL;DR

This paper demonstrates the ability to control and reconfigure the spatial distribution of supercurrents in ferromagnetic Josephson junctions by manipulating magnetic vortices, advancing superconducting spintronics technology.

Contribution

It introduces a method to tailor supercurrent pathways in ferromagnetic weak links using magnetic vortices, combining simulations and experimental validation.

Findings

Successfully designed a vortex-based structure with distinct supercurrent channels.

Controlled supercurrent pathways by moving magnetic vortices with an external field.

Validated the design through superconducting quantum interferometry measurements.

Abstract

Spin-triplet Cooper pairs induced in ferromagnets form the centrepiece of the emerging field of superconducting spintronics [1,2]. Usually the focus of research is on the spin polarization of the triplets, potentially enabling low-dissipation magnetization switching and domain wall motion. However, the fundamental mechanism for generating triplet pairs [3,4] also permits control over a parameter which has not been addressed before, namely the spatial distribution of the supercurrent. Here we demonstrate this control by tailoring distinct supercurrent pathways in the ferromagnetic weak link of a Josephson junction. Combining micromagnetic simulations with three-dimensional critical current calculations, based on the Usadel description of mesoscopic superconductivity [5], we designed a disk-shaped structure with a magnetic vortex, which induces two distinct supercurrent channels across the junction. The design was successfully tested with superconducting quantum interferometry (SQI). Moreover, we show how the position of the pathways can be controlled by moving the vortex with a magnetic field. This novel approach allows adaptable supercurrent paths to be dynamically reconfigured to switch between different functionalities in the same device.