Intrinsic peculiarities of real material realizations of a spin-1/2 kagomé lattice

Abstract

Spin-1/2 magnets with kagomé geometry, being for years a generic object of theoretical investigations, have few real material realizations. Recently, a DFT-based microscopic model for two such materials, kapellasite Cu3Zn(OH)6Cl2 and haydeeite Cu 3Mg(OH)6Cl2, was presented [Janson O, Richter J and Rosner H arxiv:0806.1592]. Here, we focus on the intrinsic properties of real spin-1/2 kagomé materials having influence on the magnetic ground state and the low-temperature excitations. We find that the values of exchange integrals are strongly dependent on O - H distance inside the hydroxyl groups, present in most spin-1/2 kagomé compounds up to date. Besides the original kagomé model, considering only the nearest neighbour exchange, we emphasize the crucial role of the exchange along the diagonals of the kagomé lattice. © 2009 IOP Publishing Ltd.