Year: 2020
Type: article
Abstract: Magnetic properties and underlying magnetic models of the synthetic ${A}_{2}{\mathrm{Cu}}_{3}\mathrm{O}{({\mathrm{SO}}_{4})}_{3}$ fedotovite ($A$ = K) and puninite ($A$ = Na) minerals, as well as the mixed euchlorine-type ${\mathrm{NaKCu}}_{3}\mathrm{O}{({\mathrm{SO}}_{4})}_{3}$ are reported. We show that all three compounds contain magnetic ${\mathrm{Cu}}_{6}$ hexamer units which at temperatures below about 100 K act as single spin-1 entities. Weak interactions between these magnetic molecules lead to long-range order below ${T}_{N}=3.4\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ ($A$ = Na), 4.7 K ($A$ = NaK), and about 3.0 K ($A$ = K). The formation of the magnetic order is elucidated by ab initio calculations that reveal two-dimensional interhexamer interactions within crystallographic $bc$ planes. This model indicates the presence of a weakly distorted square lattice of $S=1$ magnetic ions and challenges the earlier description of the ${A}_{2}{\mathrm{Cu}}_{3}\mathrm{O}{({\mathrm{SO}}_{4})}_{3}$ minerals in terms of Haldane spin chains.
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3021847005