Ga$_{x}$Cu$_{4-x}$(OD)$_{6}$Cl$_{2}$: Insulating ground state in an electron doped kagome system

TL;DR

This study synthesizes Ga$_{x}$Cu$_{4-x}$(OD)$_{6}$Cl$_{2}$, demonstrating it remains an insulating kagome system with suppressed magnetic order as Ga substitution increases, revealing insights into its magnetic and structural properties.

Contribution

The paper introduces a new synthesis method for Ga$_{x}$Cu$_{4-x}$(OD)$_{6}$Cl$_{2}$ and characterizes its magnetic, structural, and disorder properties across different Ga concentrations.

Findings

Insulating ground state persists with Ga substitution.

Long-range magnetic order is suppressed as x increases.

Ga is homogeneously distributed in the lattice.

Abstract

We present a successful synthesis method of the series Ga$_{x}$Cu$_{4-x}$(OD)$_{6}$Cl$_{2}$ with substitutions up to $x=0.8$. The compound remains a frustrated kagome system with an insulating ground state similar to herbertsmithite for these substitutions, as the additional charge of Ga$^{3+}$ is most likely bound to additional OH$^{-}$ and Cl$^{-}$. Besides infrared measurements, we present magnetic and specific-heat data down to 2 K for selected samples with $0\leq x\leq0.8$. With increasing $x$ the long-range magnetic order is suppressed, similar to what was observed in the series Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$Cl$_{2}$, indicating that Ga goes predominantly to the inter-plane position of the layered crystal structure. The reduction of the frozen magnetic fraction with increasing substitution was followed by $\mu$SR measurements. $^{69,71}$Ga nuclear magnetic resonance (NMR) was applied as a local probe for Ga induced disorder. One well resolved Ga NMR line of moderate width is found for each isotope across the phase diagram which indicates a rather homogeneous distribution of the Ga isotopes on a single site in the lattice.