Eur. Phys. J. B 59, 305-309 (2007)
https://doi.org/10.1140/epjb/e2007-00301-6

Magnetic susceptibility and specific heat of the spin- Heisenberg model on the kagome lattice and experimental data on ZnCu₃(OH)₆Cl₂

¹ Service de Physique Théorique, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
² Laboratoire de Physique Théorique de la Matière Condensée, Univ. P. et M. Curie, 75252 Paris Cedex, France

Corresponding author: ^a gregoire.misguich@cea.fr

Received: 3 July 2007
Published online: 1 November 2007

Abstract

We compute the magnetic susceptibility and specific heat of the spin- Heisenberg model on the kagome lattice with high-temperature expansions and exact diagonalizations. We compare the results with the experimental data on ZnCu₃(OH)₆Cl₂ obtained by Helton et al. [Phys. Rev. Lett. 98, 107204 (2007)]. Down to k_BT/J≃0.2, our calculations reproduce accurately the experimental susceptibility, with an exchange interaction J≃190 K and a contribution of 3.7% of weakly interacting impurity spins. The comparison between our calculations of the specific heat and the experiments indicate that the low-temperature entropy (below ~20 K) is smaller in ZnCu₃(OH)₆Cl₂ than in the kagome Heisenberg model, a likely signature of other interactions in the system.