Co-doping effects on magnetism and superconductivity in the 112-type EuFeAs2 system

TL;DR

This study explores how cobalt doping influences magnetism and superconductivity in EuFeAs2, revealing that Co induces superconductivity and affects magnetic transitions, with optimal doping levels achieving Tc up to 30.6 K.

Contribution

It provides new insights into the doping-induced evolution of magnetism and superconductivity in the 112-type EuFeAs2 system, a previously unexplored charge-neutral parent phase.

Findings

Co doping induces superconductivity with Tc up to 30.6 K.

Eu-related antiferromagnetic transition remains unaffected by Co doping.

Fe-related spin density wave transition temperature decreases rapidly with Co doping.

Abstract

The discovery of EuFeAs2, currently the only charge-neutral parent phase of the 112-type iron-pnictide system, provides a new platform for the study of elemental doping effects on magnetism and superconductivity (SC). In this study, a series of polycrystalline EuFe1-yCoyAs2 and Eu0.9Pr0.1Fe1-yCoyAs2 samples are synthesized through solid-state reaction, and the evolutions of SC and magnetism with Co doping in EuFeAs2 and Eu0.9Pr0.1FeAs2 are investigated by electrical transport and magnetic susceptibility measurements. For EuFe1-yCoyAs2, the Eu-related antiferromagnetic (AFM) transition around 40 K is barely affected by Co doping, while the Fe-related spin density wave (SDW) transition temperature drops rapidly. Meanwhile, SC is induced by a trace amount of Co doping, with a highest transition temperature Tc ~ 28 K found in EuFe0.9Co0.1As2. For the Eu0.9Pr0.1Fe1-yCoyAs2 series, the magnetism and superconductivity show similar evolutions upon Co doping, and the highest Tc is enhanced to 30.6 K with an optimum doping level y ~ 0.07. Our results shed light on the competition between SC and SDW with Co doping in the 112-type EuFeAs2 system.