# Elucidation of the helical spin structure of FeAs

## TL;DR

This paper investigates the magnetic structure of FeAs using resonant x-ray scattering and electronic calculations, revealing a more elliptical spin helix with right-handed chirality and out-of-plane moments, advancing understanding of its magnetic properties.

## Contribution

The study provides detailed insights into FeAs's magnetic structure, including the ellipticity, chirality, and out-of-plane components, supported by experimental and theoretical analysis.

## Key findings

- Ellipticity of the spin helix is 2.58(3).
- FeAs exhibits right-handed chirality.
- Electronic structure calculations explain the magnetic canting.

## Abstract

We present the results of resonant x-ray scattering measurements and electronic structure calculations on the monoarsenide FeAs. We elucidate details of the magnetic structure, showing the ratio of ellipticity of the spin helix is larger than previously thought, at 2.58(3), and reveal both a right-handed chirality and an out of plane component of the magnetic moments in the spin helix. We find that electronic structure calculations and analysis of the spin-orbit interaction are able to qualitatively account for this canting.