Exerting chemical pressure on the kagome lattice as frustration control in the kapellasite family $A$Cu$_3$(OH)$_{6+x}$(Cl,Br)$_{3-x}$

TL;DR

This study explores how chemical pressure from different rare-earth cations influences the structure and magnetic properties of kapellasite family compounds, revealing a transition to a spin liquid phase near a superstructure change.

Contribution

It demonstrates the control of magnetic frustration and spin liquid stabilization through chemical pressure and structural tuning in kagome lattice materials.

Findings

Structural transition to a superstructure at Dy cation

Distorted kagome lattice exhibits spin liquid features

Chemical pressure stabilizes the spin liquid phase

Abstract

The kapellasite family $A$Cu$_3$(OH)$_{6+x}$(Cl,Br)$_{3-x}$ forms a series of compounds, wherein the chemical pressure realized by the $A-$site cation tunes the spin exchange in the frustrated distorted kagome lattice. Via hydrothermal synthesis we have grown single crystals of the whole series for $A=$ rare-earths and found a clear structural transition to a superstructure variant at a specific chemical pressure level exerted by $A$~=~Dy. Phases with crystal structures in the vicinity of this superstructure transition realize a distorted kagome lattice of the Cu$^{2+}$ cations with characteristic features of a spin liquid. Here, subtle structural disorder as well as controlled chemical pressure can stabilize the spin liquid phase. We study the crystal structure and the magnetic ground state of these phases via single crystal x-ray diffraction, magnetic susceptibility, specific heat and muon spin spectroscopy measurements.