Spangolite: an s=1/2 maple leaf lattice antiferromagnet?

TL;DR

This paper investigates the crystal structure and magnetic properties of spangolite, revealing a complex lattice with dimerization dominating magnetic behavior despite structural trimers.

Contribution

It provides detailed structural analysis and magnetic measurements showing that magnetic properties are governed by dimerization rather than the expected lattice structure.

Findings

Magnetic susceptibility is reduced below expected levels.

The lattice comprises two species of edge-linked trimers.

Magnetic behavior is dominated by dimerization.

Abstract

Spangolite, Cu6Al(SO4)(OH)12Cl.3H2O, is a hydrated layered copper sulphate mineral. The Cu2+ ions of each layer form a systematically depleted triangular lattice which approximates a maple leaf lattice. We present details of the crystal structure, which suggest that in spangolite this lattice actually comprises two species of edge linked trimers with different exchange parameters. However, magnetic susceptibility measurements show that despite the structural trimers, the magnetic properties are dominated by dimerization. The high temperature magnetic moment is strongly reduced below that expected for the six s=1/2 in the unit cell.