New S=1/2 Kagome Antiferromagnets A$_2$Cu$_3$SnF$_{12}$: A=Cs and Rb

TL;DR

This study synthesized and characterized new Kagome antiferromagnets Cs$_2$Cu$_3$SnF$_{12}$ and Rb$_2$Cu$_3$SnF$_{12}$, revealing their magnetic properties, phase transitions, and agreement with theoretical models for $S=1/2$ Kagome systems.

Contribution

First synthesis and detailed magnetic analysis of new $S=1/2$ Kagome antiferromagnets with structural and magnetic phase transition insights.

Findings

Cs$_2$Cu$_3$SnF$_{12}$ exhibits a structural phase transition at 185 K.

Magnetic susceptibility matches theoretical models down to the transition temperature.

Cs$_2$Cu$_3$SnF$_{12}$ orders magnetically at 20 K.

Abstract

We synthesized single crystals of the new hexagonal compounds A$_2$Cu$_3$SnF$_{12}$ with A=Cs and Rb, and investigated their magnetic properties. These compounds are composed of Kagom\'{e} layers of corner-sharing CuF$_6$-octahedra. Cs$_2$Cu$_3$SnF$_{12}$ has the proper Kagom\'{e} layer at room temperature, and undergoes structural phase transition at $T_\mathrm{t}\simeq 185$ K. The temperature dependence of the magnetic susceptibility in Cs$_2$Cu$_3$SnF$_{12}$ agrees well with the result of the numerical calculation for $S=1/2$ two-dimensional Heisenberg Kagom\'{e} antiferromagnet down to $T_\mathrm{t}$ with the nearest exchange interaction $J/k_\mathrm{B}\simeq 240$ K. Although the magnetic susceptibility deviates from the calculated result below $T<T_\mathrm{t}$, the rounded maxima were observed at approximately $T\simeq (1/6)J/k_\mathrm{B}$ as predicted by the theory. Cs$_2$Cu$_3$SnF$_{12}$ undergoes three-dimensional magnetic ordering at $T_\mathrm{N} = 20$ K.