Unusual Behavior of Antiferromagnetic Superconductors in Low Magnetic Fields

TL;DR

This paper investigates the unusual behavior of antiferromagnetic superconductors in low magnetic fields, highlighting the interplay between magnetism and superconductivity, especially near phase transition temperatures, with experimental findings on Gd-based compounds.

Contribution

It reveals new insights into the magnetic-superconducting interactions in high-$T_c$ materials, particularly in Gd-based compounds, and identifies specific features near the Néel temperature.

Findings

Peak in ac susceptibility near Néel temperature for x=0.2

Suppression of superconducting currents due to magnetic fluctuations

Interaction between magnetic and conducting electrons confirmed

Abstract

In this article, we examine the superconducting properties of low- and high-$T_c$ magnetic superconductors in magnetic fields close to the first penetration field. Attention is paid to the properties that relate to the interactions between antiferromagnetism and superconductivity. It is suggested that several features characterizing the interplay between magnetic and superconducting subsystems in low-$T_c$ superconductors can also be present in high-$T_c$ materials, however, they have not been observed for any non-substituted antiferromagnetic superconductors of the Y123 type. For the Gd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-\delta}$ compound, a peak in the temperature dependence of the ac susceptibility has been found for $x = 0.2$ near the N\'{e}el temperature of the Gd sublattice. This peak is attributed to the suppression of superconducting persistent currents due to the pair breaking effect that results from the enhanced magnetic fluctuations in the vicinity of the phase transition temperature. This observation indicates that the interaction between magnetic and conducting electrons is present for the composition with $x = 0.2$, where magnetism is enhanced and superconductivity diminished.