Perfect Kagomé lattices in YCu3(OH)6Cl3: a new candidate for the quantum spin liquid state

Abstract

Polymorphs of ZnCu₃(OH)₆Cl₂ (herbertsmithite and kapellasite) and related cuprates MCu₃(OH)₆Cl₂ (M = Mg²⁺, Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Mn²⁺ and Ni²⁺) with antiferromagnetic Kagomé lattices have attracted attention for intensively investigating the quantum spin liquid (QSL) materials. However, mixing between magnetic (Cu²⁺) and diamagnetic divalent ions (Zn²⁺, Mg²⁺, etc.) is commonly significant in MCu₃(OH)₆Cl₂ and therefore disturbs the perfect Kagomé lattices consequently adversely affecting the magnetic performance. Herein we report on the synthesis and characterization of YCu₃(OH)₆Cl₃, the first-ever cuprate of the kapellasite-type structure with a trivalent cation. Single-crystal X-ray structure refinements show that the diamagnetic Y³⁺ cations in the title compound are located at the Zn positions and are charge balanced by additional Cl⁻ anions between the Kagomé layers. ⁶⁵Cu and ³⁵Cl MAS NMR analyses confirm single-crystal X-ray diffraction data that there is no detectable mixing between Y³⁺ and Cu²⁺ in the title compound, resulting in a more idealized Kagomé lattice than those in herbertsmithite and kapellasite. Magnetic analyses demonstrate that the title compound is a geometrically frustrated S = 1/2 antiferromagnet with a Curie–Weiss temperature θ of −99 K and does not show any magnetic transition down to 2 K (i.e., the frustration parameter f > 49), suggesting a possible QSL candidate.