Superconductivity Above 40 K Observed in a New Iron Arsenide Oxide (Fe2As2)(Ca4(Mg,Ti)3Oy)

TL;DR

This paper reports the discovery of a new iron arsenide oxide superconductor with a transition temperature of 43 K, the second highest among layered iron-based superconductors, achieved without doping.

Contribution

The study introduces a novel layered iron arsenide oxide with a unique crystal structure and demonstrates its bulk superconductivity at 43 K without doping.

Findings

Superconductor exhibits Tc up to 43 K.

Resistivity drops at ~47 K, zero resistance at 42 K.

Second highest Tc among layered iron-based superconductors.

Abstract

A new layered iron arsenide oxide (Fe2As2)(Ca4(Mg,Ti)3Oy) was discovered. Its crystal structure is tetragonal with a space group of I4/mmm consisted of the anti-fluorite type FeAs layer and blocking layer of triple perovskite cells and is identical with (Fe2As2)(Sr4(Sc,Ti)3O8) discovered in our previous study. The lattice constants of (Fe2As2)(Ca4(Mg,Ti)3Oy) are a = 3.877 A and c = 33.37 A. This compound exhibited bulk superconductivity up to 43 K in susceptibility measurement without intentional carrier doping. A resistivity drop was observed at ~47 K and zero resistance was achieved at 42 K. These values correspond to the second highest Tc among the layered iron-based superconductors after REFeAsO system.