# Antiferromagnetism in kagome $\alpha$-Cu$_{3}$Mg(OH)$_6$Br$_2$

## TL;DR

This study investigates the antiferromagnetic properties of $ ext{Cu}_3 ext{Mg}( ext{OH})_6 ext{Br}_2$, revealing its magnetic ordering at 5.4 K and suggesting it as a realization of the 2D spin-1/2 Heisenberg kagome model near the ferromagnetic phase.

## Contribution

The paper provides experimental evidence of antiferromagnetic order in $ ext{Cu}_3 ext{Mg}( ext{OH})_6 ext{Br}_2$ and links it to the theoretical kagome Heisenberg model, highlighting its position near the ferromagnetic phase boundary.

## Key findings

- Antiferromagnetic order at 5.4 K with moments aligned ferromagnetically within kagome planes.
- Ordered magnetic moment of 0.94 μ_B indicates minimal quantum and geometrical fluctuations.
- Comparison with haydeeite suggests the material is near the ferromagnetic side of the kagome phase diagram.

## Abstract

The antiferromagnetism in $\alpha$-Cu$_3$Mg(OH)$_6$Br$_2$ was studied by magnetic-susceptibility, specific-heat and neutron-diffraction measurements. The crystal structure consists of Cu$^{2+}$ kagome layers with Mg$^{2+}$ ions occupying the centers of the hexagons, separated by Br$^{1-}$ ions. The magnetic system orders antiferromagnetically at 5.4 K with the magnetic moments aligned ferromagnetically within the kagome planes. The ordered moment is 0.94 $\mu_B$, suggesting little quantum and geometrical fluctuations. By comparing the magnetic and specific-heat properties with those of the haydeeite, we suggest that $\alpha$-Cu$_3$Mg(OH)$_6$Br$_2$ may be described by the two-dimensional spin-$1/2$ Heisenberg kagome model and is in the region of the ferromagnetic-order side of the phase diagram.