Vortex Plasma in a Superconducting Film with Magnetic Dots

TL;DR

This paper investigates how magnetic dots influence vortex concentration in a superconducting film, revealing step-like and oscillatory behaviors dependent on the dots' magnetization at low temperatures.

Contribution

It introduces a model for vortex behavior in superconducting films with magnetic dot arrays, highlighting the dependence on magnetic moment and dot density.

Findings

Vortex concentration bound to dots is proportional to dot density.

Unbound vortex concentration oscillates with magnetic moment.

Vortex behavior exhibits step-like and oscillatory patterns.

Abstract

We consider a superconducting film, placed upon a magnetic dot array. Magnetic moments of the dots are normal to the film and randomly oriented. We determine how the concentration of the vortices in the film depends on the magnetic moment of a dot at low temperatures. The concentration of the vortices, bound to the dots, is proportional to the density of the dots and depends on the magnetization of a dot in a step-like way. The concentration of the unbound vortices oscillates about a value, proportional to the magnetic moment of the dots. The period of the oscillations is equal to the width of a step in the concentration of the bound vortices.