# Local magnetism, magnetic order and spin freezing in the 'nonmetallic metal' FeCrAs

## TL;DR

This study investigates the magnetic structure and dynamics of FeCrAs using x-ray scattering, muon-spin relaxation, and density functional theory, revealing complex magnetic order, fluctuations, and disorder effects.

## Contribution

It provides detailed experimental and theoretical insights into the magnetic order, fluctuations, and muon stopping sites in FeCrAs, a nonmetallic metal with unusual magnetic properties.

## Key findings

- Magnetic x-ray scattering confirms 120° non-collinear antiferromagnetic order.
- Muon-spin relaxation shows magnetic ordering below 105 K and signs of spin fluctuations above.
- Density functional theory identifies muon stopping sites and assesses local distortions.

## Abstract

We present the results of x-ray scattering and muon-spin relaxation ($\mu^{+}$SR) measurements on the iron-pnictide compound FeCrAs. Polarized non-resonant magnetic x-ray scattering results reveal the 120$^\circ$ periodicity expected from the suggested three-fold symmetric, non-collinear antiferromagnetic structure. $\mu^+$SR measurements indicate a magnetically ordered phase throughout the bulk of the material below $T_\mathrm{N}$=105(5) K. There are signs of fluctuating magnetism in a narrow range of temperatures above $T_\mathrm{N}$ involving low-energy excitations, while at temperatures well below $T_\mathrm{N}$ behaviour characteristic of freezing of dynamics is observed, likely reflecting the effect of disorder in our polycrystalline sample. Using density functional theory we propose a distinct muon stopping site in this compound and assess the degree of distortion induced by the implanted muon.