Magnetic and Crystallographic Studies of Mg-Herbertsmithite, γ-Cu₃Mg(OH)₆Cl₂—A New S = 1/2 Kagome Magnet and Candidate Spin Liquid

Studies are presented of the synthesis, crystal structure, and magnetic properties of the new quantum kagome magnet Mg-herbertsmithite, γ-Cu 3 Mg(OH) 6 Cl 2 . The material features strong antiferromagnetic exchange characterized by a Weiss temperature of θ W ≃ −284 K and a gradual buildup of short-ranged antiferromagnetic correlations upon cooling. No magnetic transition is observed until T C ≃ 4−5 K when a small ferromagnetic component orders; susceptibility measurements indicate that this transition is due to an impurity and that there is no evidence of a magnetic transition in the herbertsmithite phase whose spins appear to remain dynamic down to the lowest temperatures studied.