Magnetic susceptibility and specific heat of the spin - 12 Heisenberg model on the kagome lattice and experimental data on

We compute the magnetic susceptibility and specific heat of the spin1 2 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 kBT/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 lowtemperature 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. PACS. 75.50.Ee Antiferromagnetics – 75.10.Jm Quantized spin models – 75.40.Cx Static properties