Superconductivity and ferromagnetism in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$

TL;DR

This study demonstrates the coexistence of superconductivity and ferromagnetism in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$, revealing their compatibility in a specific doping range and highlighting the roles of Fe-3$d$ electrons and Eu-4$f$ moments.

Contribution

It provides experimental evidence of coexistence of superconductivity and ferromagnetism in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$, emphasizing the robustness and multi-orbital nature of iron pnictides.

Findings

Superconductivity coexists with ferromagnetism in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ for 0.2 ≤ x ≤ 0.4.

Coexistence features include large ferromagnetic moments and comparable transition temperatures.

The phenomenon is attributed to the robustness of superconductivity and multi-orbital effects.

Abstract

Superconductivity and ferromagnetism are two antagonistic cooperative phenomena, which makes it difficult for them to coexist. Here we demonstrate experimentally that they do coexist in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ with $0.2\leq x\leq0.4$, in which superconductivity is associated with Fe-3$d$ electrons and ferromagnetism comes from the long-range ordering of Eu-4$f$ moments via Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. The coexistence is featured by large saturated ferromagnetic moments, high and comparable superconducting and magnetic transition temperatures, and broad coexistence ranges in temperature and field. We ascribe this unusual phenomenon to the robustness of superconductivity as well as the multi-orbital characters of iron pnictides.