Influence of the stray field of magnetic dot on the nucleation of superconductivity in a disk

TL;DR

This study explores how the inhomogeneous stray magnetic field from a magnetic dot influences the nucleation of superconductivity in a mesoscopic aluminum disk, revealing a maximum critical temperature at a specific applied magnetic field.

Contribution

It provides experimental and theoretical analysis of superconductivity nucleation in a hybrid structure with a magnetic dot, highlighting the role of inhomogeneous magnetic fields.

Findings

Maximum critical temperature occurs at a finite applied magnetic field.

Good agreement between experimental data and Ginzburg-Landau theory.

Inhomogeneous magnetic field affects superconductivity nucleation.

Abstract

We have investigated the nucleation of superconductivity in an Al mesoscopic disk, with a magnetic dot on the top. The dot is magnetized perpendicularly, and its magnetic field is inhomogeneous. The Al disk and magnetic dot are separated by an insulating layer, which ensures that there is only magnetic interaction between them. This hybrid superconductor/ferromagnet structure exhibits the maximum critical temperature for a finite value of the perpendicular applied magnetic field, which is parallel to the magnetization of magnetic dot. We have found a good agreement between the experimental data for the superconductor/normal metal phase boundary and the theoretical predictions based on the Ginzburg-Landau theory.