Comparative investigation of the coupled-tetrahedra quantum spin systems Cu2Te2O5X2, X=Cl, Br and Cu4Te5O12Cl4

TL;DR

This study compares the magnetic properties of coupled-tetrahedra quantum spin systems Cu-2252(X) and Cu-45124(Cl) using ab initio calculations, revealing how structural differences influence their phase transition temperatures.

Contribution

It provides a detailed ab initio analysis of the structural and magnetic differences between known and newly synthesized coupled-tetrahedra spin systems, including predictions for a not yet synthesized compound.

Findings

Cu-45124(Cl) has a lower critical temperature than Cu-2252(Cl).

Structural modifications affect magnetic interaction pathways.

Predicted behavior of Cu-45124(Br) based on relaxed structure.

Abstract

We present a comparative study of the coupled-tetrahedra quantum spin systems Cu2Te2O5X2, X=Cl, Br (Cu-2252(X)) and the newly synthesized Cu4Te5O12Cl4 (Cu-45124(Cl)) based on ab initio Density Functional Theory calculations. The magnetic behavior of Cu-45124(Cl) with a phase transition to an ordered state at a lower critical temperature T$_c$=13.6K than in Cu-2252(Cl) (T$_c$=18K) can be well understood in terms of the modified interaction paths. We identify the relevant structural changes between the two systems and discuss the hypothetical behavior of the not yet synthesized Cu-45124(Br) with an ab initio relaxed structure using Car-Parrinello Molecular Dynamics.