Magnetic properties of frustrated two-dimensional S=1/2 antiferromagnets on a square lattice

An overview of the basic magnetic properties of vanadates which represent prototypes of frustrated two-dimensional S = 1/2 antiferromagnets on a square lattice is presented. It will be shown how information on the ground state sublattice magnetization, on the static uniform susceptibility and on the frustration driven lattice distortions can be achieved by means of NMR spectroscopy and magnetization measurements. The low-energy spin excitations, investigated by means of NMR and muSR relaxation measurements, will be analysed and the anomalous very-low-frequency dynamics, originating from the degeneracy of the ground state, discussed. Finally the effects of hydrostatic pressure on the degree of frustration of the vanadates will be addressed.