# An in-plane hexagonal antiferromagnet in the Cu-Mn-As system, Cu$_{0.82}$Mn$_{1.18}$As

## TL;DR

This paper reports the synthesis and detailed characterization of a new hexagonal antiferromagnetic phase, Cu$_{0.82}$Mn$_{1.18}$As, with unique magnetic and electronic properties, expanding understanding of antiferromagnetic materials in the Cu-Mn-As system.

## Contribution

It introduces a new hexagonal Cu-Mn-As phase, providing insights into its magnetic structure, electronic behavior, and potential as a control material for Néel switching studies.

## Key findings

- Antiferromagnetic ordering at 270 K.
- Triangular in-plane spin arrangement.
- Weak resistivity variation from 5 K to 300 K.

## Abstract

We report the single-crystal growth and characterization of a new hexagonal phase, Cu$_{0.82}$Mn$_{1.18}$As, in the Cu-Mn-As system. This compound contains the same square-pyramidal MnAs$_5$ units as the tetragonal and orthorhombic polymorphs of CuMnAs. Calorimetry, magnetometry, and neutron diffraction measurements reveal antiferromagnetic ordering at 270 K. The magnetic structure consists of a triangular arrangement of spins in the $ab$ plane. Hexagonal Cu$_{0.82}$Mn$_{1.18}$As shows resistivity that varies only weakly from 5 K to 300 K, and is many times higher than tetragonal CuMnAs, indicative of a strongly-scattering metal. First-principles calculations confirm the metallic band structure with a small density of states at the Fermi energy. The neutron-refined magnetic ground state is close to the computationally-determined minimum energy configuration. This compound should serve as a clear control when disentangling the effects of current-driven N\'{e}el switching of metallic antiferromagnets since it exhibits in-plane spins but the magnetic ordering does not break degeneracy along the $a$ and $b$ directions, unlike tetragonal CuMnAs.