New iron-based arsenide oxides (Fe2As2)(Sr4M2O6)(M = Sc, Cr)

TL;DR

This paper reports the discovery and structural characterization of new iron-based arsenide oxides with layered structures, highlighting their unique lattice parameters and chemical flexibility, but noting the absence of superconductivity due to low carrier concentration.

Contribution

The study introduces novel layered oxyarsenides (Fe2As2)(Sr4M2O6) with M = Sc, Cr, expanding the family of iron-based oxypnictides and analyzing their structural and chemical properties.

Findings

Longest interlayer Fe-Fe distance in iron-based oxypnictides

Structural differences compared to REFePnO systems

No superconductivity observed due to low carrier concentration

Abstract

We have discovered new layered oxyarsenides (Fe2As2)(Sr4M2O6) (M = Sc, Cr: M-22426). These materials are isostructural with (Fe2P2)(Sr4Sc2O6), which was found in our previous study. The new compounds are tetragonal with a space group of P4/nmm and consist of the anti-fluorite type FeAs layer and perovskite-type blocking layer. The lattice constants are a = 4.050 A, c = 15.809 A for M = Sc and a = 3.918 A, c = 15.683 A for M = Cr. These compounds have long interlayer Fe-Fe distances corresponding to the c-axis length, the 15.8 A in Sc-22426 is the longest in the iron-based oxypnictide systems. Chemical flexibility of the perovskite block in this system was probed by chromium containing (Fe2As2)(Sr4Cr2O6). Different trends were found in bond angle and bond length of the new oxypnictides compared to the reported systems, such as REFePnO. Absence of superconductivity in these compounds is considered to be due to insufficient carrier concentration as in the case of undoped REFeAsO.