Superconductivity at 22.3 K in SrFe2-xIrxAs2

TL;DR

This paper reports the synthesis of a new iron-based superconductor SrFe2-xIrxAs2 with a transition temperature of 22.3 K, demonstrating the effects of Ir doping on its structure and superconducting properties.

Contribution

It introduces a novel Ir-doped SrFe2As2 superconductor with detailed structural and superconducting characterization, expanding understanding of doping effects in iron pnictides.

Findings

Superconductivity at 22.3 K in SrFe2-xIrxAs2.

High Meissner shielding volume indicating bulk superconductivity.

Upper critical field estimated at about 58 T.

Abstract

By substituting the Fe with the 5d-transition metal Ir in SrFe2As2, we have successfully synthesized the superconductor SrFe2-xIrxAs2 with Tc = 22.3 K at x = 0.5. X-ray diffraction indicates that the material has formed the ThCr2Si2-type structure with a space group I4/mmm. The temperature dependence of resistivity and dc magnetization both reveal sharp superconducting transitions at around 22 K. An estimate on the diamagnetization signal reveals a high Meissner shielding volume. Interestingly, the normal state resistivity exhibits a roughly linear behavior up to 300 K. The superconducting transitions at different magnetic fields were also measured yielding a slope of -dHc2/dT = 3.8 T/K near Tc. Using the Werthamer-Helfand-Hohenberg (WHH) formula, the upper critical field at zero K is found to be about 58 T. Counting the possible number of electrons doped into the system in SrFe2-xIrxAs2, we argue that the superconductivity in the Ir-doped system is different from the Co-doped case, which should add more ingredients to the underlying physics of the iron pnictide superconductors.