The layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs

TL;DR

This study synthesizes and characterizes layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs, revealing their crystal structures, magnetic properties, and the absence of spin-density wave anomalies, with insights into their magnetic behavior.

Contribution

First detailed structural and magnetic characterization of Sr2CrO3FeAs and Ba2ScO3FeAs, highlighting their unique layered structures and magnetic properties compared to other iron arsenides.

Findings

Structures are tetragonal and isotypic to Sr2ScO3CuS.

No spin-density wave anomalies observed.

Sr2CrO3FeAs shows antiferromagnetic ordering below 31 K.

Abstract

Polycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-ray powder diffraction. Their structures are tetragonal (P4/nmm; Sr2CrO3FeAs: a = 391.12(1) pm, c = 1579.05(3) pm; Ba2ScO3FeAs: a = 412.66(5) pm, c = 1680.0(2) pm, Z = 2) and isotypic to Sr2ScO3CuS. Iron arsenide layers are sandwiched between perowskite-like oxide blocks and separated by ~1600 pm, which is much larger compared to the 1111 iron arsenide superconductors. The bond length and angles within the FeAs layers are adapted to the space requirements of the oxide blocks. Measurements of the magnetic susceptibility and electrical resistivity show no hint for a SDW-like anomaly in both compounds. Sr2CrO3FeAs shows Curie-Weiss paramagnetism above 160 K with an effective magnetic moment of 3.83(3) muB in good agreement with the theoretical value of 3.87 muB for Cr3+. Antiferromagnetic ordering was detected below TN ~ 31 K. 57Fe Moessbauer spectra of Sr2CrO3FeAs show a single signal that broadens below the magnetic ordering temperature due to a small transferred hyperfine field induced by the magnetic ordering of the chromium atoms. 57Fe-Moessbauer spectra of Ba2ScO3FeAs show single signals at 298, 77, and 4.2 K which are only subject to weak quadrupole splitting.