Cobalt-substitution-induced Superconductivity in a New Compound with ZrCuSiAs-type Structure, SrFeAsF

TL;DR

This study reports the synthesis of a new SrFeAsF compound with a ZrCuSiAs-type structure, where Co substitution induces superconductivity at 4 K, highlighting the role of interlayer interactions in FeAs-based superconductors.

Contribution

The paper introduces a new SrFeAsF compound and demonstrates that Co substitution induces superconductivity, emphasizing the significance of interlayer interactions for Tc in FeAs-based materials.

Findings

SrFeAsF has a ZrCuSiAs-type structure with metallic conduction.

Partial Co substitution suppresses anomalies and induces superconductivity.

Max Tc observed is 4 K for SrFe0.875Co0.125AsF.

Abstract

We have synthesized a quaternary fluoroarsenide SrFeAsF with the ZrCuSiAs-type structure (P4/nmm, a = 0.3999 and c = 0.8973 nm), which is composed of an alternately stacked (FeAs)- and (SrF)+ layers, analogous to the FeAs-based superconductor LaFeAsO. SrFeAsF shows metallic type conduction with the anomaly at ~180 K. The partial replacement of the Fe with Co suppresses the anomaly and induces the superconductivity, while the maximal Tc (4 K for SrFe0.875Co0.125AsF) is much lower than that of the Co-substituted LaFeAsO. Replacement of (LaO)+ layers with (SrF)+ layers results in a enlargement of the c-axis length (+2.6%). These results suggest the importance of interlayer interaction as a critical Tc-controlling factor in FeAs-based superconductors.