Magnetic competition in iron-based germanide and silicide superconductors

TL;DR

This study investigates how substituting elements in iron-based superconductors affects their magnetic tendencies and potential for enhanced superconductivity, highlighting the role of spacer ions and pressure.

Contribution

It demonstrates that controlling spacer ions can suppress ferromagnetism and potentially improve superconductivity in Fe-based compounds.

Findings

Substitutions with Ge or Si induce ferromagnetic tendencies.

Controlling spacer ions effectively suppresses ferromagnetism.

Pressure suppresses ferromagnetism in YFe₂Ge₂, possibly enhancing superconductivity.

Abstract

We address the ferromagnetic tendencies detrimental for superconductivity that are related to the substitution of the pnictogen As atom with Ge or Si, together with additional substitutions in the spacer layers in 122 and 1111 Fe-based superconductors. Intermediate compounds in which these substitutions are realized individually are studied within density functional theory. We thus single out the control of spacer ions as an effective way to handle such a ferromagnetism, and we also show that it is suppressed in YFe$_2$Ge$_2$ under pressure ---which then can be expected to enhance its superconductivity.