First-principles characterization of the magnetic properties of Cu$_2$(OH)$_3$Br

TL;DR

This study uses first-principles calculations to analyze the magnetic properties of Cu2(OH)3Br, revealing the dominant steric effects of halogen ions on its magnetic behavior and providing insights into quantum spin liquids.

Contribution

It presents a comprehensive first-principles analysis of Cu2(OH)3Br's magnetic properties, combining density functional theory, spin-wave theory, and exact diagonalization for the first time.

Findings

Spectral functions match inelastic neutron scattering data

Steric effects of halogen ions dominate over chemical effects

Insights into magnetic interactions in quasi-2D spin-1/2 systems

Abstract

Low dimensional spin-1/2 transition metal oxides and oxyhalides continue to be at the forefront of research investigating nonclassical phases such as quantum spin liquids. In this study, we examine the magnetic properties of the oxyhalide $\text{Cu}_2\text{(OH)}_3\text{Br}$ in the botallackite structure using first-principles density functional theory, linear spin-wave theory, and exact diagonalization calculations. This quasi-2D system consists of $\text{Cu}^{2+}$ $\mathrm{S} = 1/2$ moments arranged on a distorted triangular lattice. Our exact diagonalization calculations, which rely on a first-principles-based magnetic model, generate spectral functions consistent with inelastic neutron scattering (INS) data. By performing computational experiments to disentangle the chemical and steric effects of the halide ions, we find that the dominant effect of the halogen ions is steric in the $\text{Cu}_2\text{(OH)}_3\text{X}$ series of compounds.