A novel reentrant susceptibility due to vortex and magnetic dipole interaction in a La1.85Sr0.15CuO4 and Gd2O3 composite system

TL;DR

This paper reports a new reentrant magnetic susceptibility behavior in a La1.85Sr0.15CuO4 and Gd2O3 composite, caused by vortex-dipole interactions leading to ferromagnetic dimer formation at low temperatures.

Contribution

It introduces a novel reentrant susceptibility phenomenon linked to vortex and magnetic dipole interactions in a superconductor-insulator composite system.

Findings

Reentrant susceptibility observed at low temperatures.

Exponential temperature dependence of excess susceptibility.

Ferromagnetic dimers form due to vortex-dipole interactions.

Abstract

A reentrant behavior of temperature dependent magnetic ac-susceptibility (or excess susceptibility(ES)) at lower temperature is observed in a composite made of superconductor $La_{1.85}Sr_{0.15}CuO_4$ (LCu) and an insulating paramagnetic salt $Gd_2O_3$ (GdO). The ES exhibits an exponential characteristic that varies with temperature ($\exp,[\frac{T_0}{T}]$), T0 is characteristics temperature. The characteristics temperature,T$_0$, decreases as the effective interface diminishes and the amplitude of the dc magnetic field increases. The creation of ferromagnetic dimers between Gd$^{+3}$ ions in GdO is observed as a result of vortex-dipole interaction, which causes the observation of this unusual ES at temperatures much lower than the superconducting onset temperature T$_{S}^{onset}$. This type of ferromagnetic dimer formation much below superconducting transition temperature is found comparable with the formation of Yu-Shiba-Rusinov (YSR) state and interaction between these YSR state.