The stable phases of the Cs2CuCl4-xBrx mixed systems

TL;DR

This study investigates the structural phase variations in Cs2CuCl4-xBrx mixed crystals grown from aqueous solutions, revealing temperature-dependent phase stability and detailed compositional effects on lattice parameters relevant to magnetic interactions.

Contribution

It provides new insights into the temperature-dependent phase stability and structural variations in Cs2CuCl4-xBrx mixed systems, including the discovery of a tetragonal phase at room temperature.

Findings

Intermediate compositions exhibit a new tetragonal phase at room temperature.

Increasing growth temperature extends orthorhombic phase stability across the entire system.

Lattice parameter analysis informs on ion site incorporation affecting magnetic properties.

Abstract

Starting from Cs2CuCl4 and Cs2CuBr4 our project focuses on the growth of the Cs2CuCl4-xBrx mixed crystals from aqueous solution and the investigation of the occurring structural variations. The well known orthorhombic structure (space group Pnma) of the end members of this system is interrupted within the intermediate composition range Cs2CuCl3Br1 - Cs2CuCl2Br2, if the growth takes place at room temperature. Within this range a new tetragonal phase is found (space group I4/mmm). However, in case the growth temperature will be increased to 50 {\deg}C, the existence of the orthorhombic structure can be extended over the whole Cs2CuCl4-xBrx mixed system. A detailed analysis of the composition dependence of the lattice parameters is used to draw conclusions on the incorporation of Cl- and Br-ions at different sites which is important for the magnetic interactions between the Cu-ions.