Spin-1/2 Kagomé-Like Lattice in Volborthite Cu3V2O7(OH)2·2H2O

Abstract
A novel cuprate Volborthite, Cu 3 V 2 O 7 (OH) 2 ·2H 2 O, containing an S -1/2 (Cu 2+ spin) kagomé -like lattice is studied by magnetic susceptibility, specific heat, and 51 V NMR measurements. Signs for neither long-range order nor spin-gapped singlet ground states are detected down to 1.8 K, in spite of large antiferromagnetic couplings of ∼100 K between Cu spins forming a two-dimensional kagomé -like network. It is suggested that Volborthite represents a system close to a quantum critical point between classical long-range ordered and quantum disordered phases.