The magnetic and crystal structure of azurite Cu$_3$(CO$_3$)$_2$(OH)$_2$ as determined by neutron diffraction

TL;DR

This study uses neutron diffraction to analyze azurite's crystal and magnetic structures, revealing a lower symmetry space group, specific magnetic moments, and the influence of strain on its magnetic properties.

Contribution

First neutron diffraction analysis of azurite showing a lower symmetry space group and detailed magnetic structure, highlighting the role of strain and anisotropic interactions.

Findings

A lower symmetry space group $P2_1$ was identified.

Magnetic moments of 0.68 and 0.25 μ_B on copper sites.

Strain strongly influences the magnetic behavior.

Abstract

Here we present neutron diffraction results on the mineral azurite. We have found that the crystal structure of azurite can be described in the space group $P2_1$ which is the next lower symmetric group of $P2_1/c$ as found in earlier work. This small change in symmetry does not greatly influence the lattice parameters or atomic fractional coordinates which are presented here for single crystal diffraction refinements. The ordered magnetic moment structure of this material has been determined and is comprised of two inequivalent magnetic moments on copper sites of magnitude 0.68(1) and 0.25(1) $\mu_{B}$. This result is discussed in terms of the anisotropic exchange and Dzyaloshinskii-Moriya interactions. It is found that the system is likely governed by one-dimensional behaviour despite the long-range ordered ground state. We also highlight the significance of strain in this material which is strongly coupled to the magnetism.