Magnetic susceptibility and specific heat of the spin-1/2 Heisenberg model on the kagome lattice and experimental data on ZnCu3(OH)6Cl2

摘要

We compute the magnetic susceptibility and specific heat of the spin-1/2Heisenberg model on the kagome lattice with high-temperature expansions andexact diagonalizations. We compare the results with the experimental data onZnCu3(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 experimentalsusceptibility, with an exchange interaction J~190K and a contribution of 3.7%of weakly interacting impurity spins. The comparison between our calculationsof the specific heat and the experiments indicate that the low-temperatureentropy (below ~20K) is smaller in ZnCu3(OH)6Cl2 than in the kagome Heisenbergmodel, a likely signature of other interactions in the system.