Ultrasensitive interplay between ferromagnetism and superconductivity in NbGd composite thin films

TL;DR

This study investigates the delicate balance and interaction between ferromagnetism and superconductivity in NbGd composite thin films, revealing how Gd doping influences the superconducting transition and magnetic properties.

Contribution

It provides new insights into the interplay between ferromagnetism and superconductivity in NbGd films, highlighting the effects of Gd concentration on phase transitions and magnetic behavior.

Findings

Superconductivity is suppressed above a critical Gd concentration.

Paramagnetic Meissner effect appears near the superconducting transition.

Magnetic signatures are evident even at very low Gd doping levels.

Abstract

A model binary hybrid system composed of a randomly distributed rare-earth ferromagnetic (Gd) part embedded in an s-wave superconducting (Nb) matrix is being manufactured to study the interplay between competing superconducting and ferromagnetic order parameters. The normal metallic to superconducting phase transition appears to be very sensitive to the magnetic counterpart and the modulation of the superconducing properties follow closely to the Abrikosov-Gorkov (AG) theory of magnetic impurity induced pair breaking mechanism. A critical concentration of Gd is obtained for the studied NbGd based composite films (CFs) above which superconductivity disappears. Besides, a magnetic ordering resembling the paramagnetic Meissner effect (PME) appears in DC magnetization measurements at temperatures close to the superconducting transition temperature. The positive magnetization related to the PME emerges upon doping Nb with Gd. The temperature dependent resistance measurements evolve in a similar fashion with the concentration of Gd as that with an external magnetic field and in both the cases, the transition curves accompany several intermediate features indicating the traces of magnetism originated either from Gd or from the external field. Finally, the signatures of magnetism appear evidently in the magnetization and transport measurements for the CFs with very low (less than 1 at. %) doping of Gd.