Effect of Co doping and hydrostatic pressure on SrFe2As2

TL;DR

This study investigates how Co doping and hydrostatic pressure influence superconductivity in SrFe2As2, revealing that both methods suppress magnetic order and induce superconductivity, with Co doping providing a more robust SC state.

Contribution

It provides a detailed phase diagram showing the effects of Co doping and pressure on superconductivity in SrFe2As2, highlighting their combined influence on the SC phase.

Findings

Maximum T_c of 20 K at 0.75 GPa for x=0.2

Superconductivity suppressed at higher Co concentrations

Pressure and doping effects are interconnected in phase behavior

Abstract

We report a pressure study on electron doped SrFe$_{2-x}$Co$_x$As$_2$ by electrical-resistivity ($\rho$) and magnetic-susceptibility ($\chi$) experiments. Application of either external pressure or Co substitution rapidly suppresses the spin-density wave ordering of the Fe moments and induces superconductivity in SrFe$_2$As$_2$. At $x=0.2$ the broad superconducting (SC) dome in the $T-p$ phase diagram exhibits its maximum $T_{c,{\rm max}}=20$ K at a pressure of only $p_{\rm max}\approx 0.75$ GPa. In SrFe$_{1.5}$Co$_{0.5}$As$_2$ no superconductivity is observed anymore up to 2.8 GPa. Upon increasing the Co concentration the maximum of the SC dome shifts toward lower pressure accompanied by a decrease in the value of $T_{c,{\rm max}}$. Even though, superconductivity is induced by both tuning methods, Co substitution leads to a much more robust SC state. Our study evidences that in SrFe$_{2-x}$Co$_x$As$_2$ both, the effect of pressure and Co-substitution, have to be considered in order to understand the SC phase-diagram and further attests the close relationship of SrFe$_2$As$_2$ and its sister compound BaFe$_2$As$_2$.