# Antiferromagnetic structure and electronic properties of BaCr2As2 and BaCrFeAs2

## TL;DR

This study investigates the antiferromagnetic and electronic properties of BaCr2As2 and BaCrFeAs2, revealing their magnetic structures, metallic nature, and the effects of atomic disorder and magneto-structural coupling.

## Contribution

It provides detailed experimental and theoretical insights into the magnetic ordering and electronic behavior of these chromium-arsenide compounds, highlighting their potential as parent materials for superconductivity.

## Key findings

- BaCr2As2 exhibits G-type antiferromagnetic order at 580 K.
- BaCrFeAs2 shows G-type order below 265 K with small Fe moments.
- Both compounds are metallic with enhanced specific heat coefficients.

## Abstract

The chromium arsenides BaCr2As2 and BaCrFeAs2 with ThCr2Si2 type structure (space group I4/mmm; also adopted by '122' iron arsenide superconductors) have been suggested as mother compounds for possible new superconductors. DFT-based calculations of the electronic structure evidence metallic antiferromagnetic ground states for both compounds. By powder neutron diffraction we confirm for BaCr2As2 a robust ordering in the antiferromagnetic G-type structure at T_N = 580 K with mu_Cr = 1.9 mu_B at T = 2K. Anomalies in the lattice parameters point to magneto-structural coupling effects. In BaCrFeAs2 the Cr and Fe atoms randomly occupy the transition-metal site and G-type order is found below 265 K with mu_Cr/Fe = 1.1 mu_B. 57Fe Moessbauer spectroscopy demonstrates that only a small ordered moment is associated with the Fe atoms, in agreement with electronic structure calculations with mu_Fe ~ 0. The temperature dependence of the hyperfine field does not follow that of the total moments. Both compounds are metallic but show large enhancements of the linear specific heat coefficient gamma with respect to the band structure values. The metallic state and the electrical transport in BaCrFeAs2 is dominated by the atomic disorder of Cr and Fe and partial magnetic disorder of Fe. Our results indicate that Neel-type order is unfavorable for the Fe moments and thus it is destabilized with increasing iron content.