Magnetic susceptibility and specific heat of the spin-<InlineEquation ID="Equ1"> <EquationSource Format="TEX">${\frac{1}{2}}$</EquationSource> </InlineEquation> Heisenberg model on the kagome lattice and experimental data on ZnCu<Subscript>3</Subscript>(OH)<Subscript>6</Subscript>Cl<Subscript>2</Subscript>

We compute the magnetic susceptibility and specific heat of the spin-<InlineEquation ID="Equ2"> <EquationSource Format="TEX">$\frac{1}{2}$</EquationSource> </InlineEquation> Heisenberg model on the kagome lattice with high-temperature expansions and exact diagonalizations. We compare the results with the experimental data on ZnCu<Subscript>3</Subscript>(OH)<Subscript>6</Subscript>Cl<Subscript>2</Su bscript> obtained by Helton et al. [Phys. Rev. Lett. <Emphasis Type="Bold">98, 107204 (2007)]. Down to k<Subscript>B</Subscript>T/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 ZnCu<Subscript>3</Subscript>(OH)<Subscript>6</Subscript>Cl<Subscript>2</Su bscript> than in the kagome Heisenberg model, a likely signature of other interactions in the system. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007