Efect of magnetic Gd impurities on superconductivity in MoGe films with different thickness and morphology

TL;DR

This study investigates how magnetic Gd impurities affect superconductivity in amorphous MoGe films of varying thickness and morphology, revealing surface effects and anisotropy influence impurity pair-breaking.

Contribution

It provides new insights into the thickness-dependent magnetic impurity effects and the role of surface-induced anisotropy in amorphous superconducting films.

Findings

Pair-breaking strength decreases with thickness in uniform films

Surface-induced magnetic anisotropy influences superconductivity suppression

Anomalous zero pair-breaking observed in thin films on SiN

Abstract

We studied the effect of magnetic doping with Gd atoms on the superconducting properties of amorphous Mo70Ge30 films. We observed that in uniform films deposited on amorphous Ge, the pair-breaking strength per impurity strongly decreases with film thickness initially and saturates at a finite value in films with thickness below the spin-orbit scattering length. The variation is likely caused by surface induced magnetic anisotropy and is consistent with the fermionic mechanism of superconductivity suppression. In thin films deposited on SiN the pair-breaking strength becomes zero. Possible reasons for this anomalous response are discussed. The morphological distinctions between the films of the two types were identified using atomic force microscopy with a carbon nanotube tip.