Tuning of a Kagome Magnet: Insulating Ground State in Ga-Substituted Cu4(OH)6Cl2

Here, a successful synthesis method of the series GaxCu4-x(OD)(6)Cl-2 with substitutions up to x = 0.8 is presented. The compound remains a frustrated kagome system with an insulating ground state similar to herbertsmithite for these substitutions, as the additional charge of Ga3+ 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 <= x <= 0.8. With increasing x the long-range magnetic order is suppressed, similar to what is observed in the series ZnxCu4-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 is followed by muon spin relaxation (mu SR) measurements. Ga-69,Ga-71 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.