Field-enhanced critical parameters in magnetically nanostructured superconductors

TL;DR

This study uses Ginzburg-Landau theory to show how magnetic nanostructuring enhances superconductivity by increasing critical parameters through vortex-antivortex interactions, aligning with recent experimental findings.

Contribution

It demonstrates theoretically how magnetic nanostructures can enhance superconducting critical parameters and explains experimental observations of field-shifted critical current characteristics.

Findings

Enhanced critical magnetic field and current due to magnetic dot arrays.

Identification of peaks in the Hext-T boundary at matching fields.

Prediction of field-shifted jc-Hext characteristics consistent with experiments.

Abstract

Within the phenomenological Ginzburg-Landau theory, we demonstrate the enhancement of superconductivity in a superconducting film, when nanostructured by a lattice of magnetic particles. Arrays of out-of-plane magnetized dots (MDs) extend the critical magnetic field and critical current the sample can sustain, due to the interaction of the vortex-antivortex pairs and surrounding supercurrents induced by the dots and the external flux lines. Depending on the stability of the vortex-antivortex lattice, a peak in the Hext-T boundary is found for applied integer and rational matching fields, which agrees with recent experiments [Lange et al., Phys. Rev. Lett. 90, 197006 (2003)]. Due to compensation of MDs- and Hext-induced currents, we predict the field-shifted jc-Hext characteristics, as was actually realized in previous experiment but not commented on [Morgan and Ketterson, Phys. Rev. Lett. 80, 3614 (1998)].