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

摘要

We compute the magnetic susceptibility and specific heat of the spin-1/2 Heisenberg model on the kagome lattice with high-temperature expansions and exact diagonalizations. We compare the results with the experimental data on ZnCu3(OH)(6)Cl-2 obtained by Helton et al. [Phys. Rev. Lett. 98, 107204 (2007)]. Down to k(B)T/J similar or equal to 0.2, our calculations reproduce accurately the experimental susceptibility, with an exchange interaction J similar or equal to 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 similar to 20 K) is smaller in ZnCu3(OH)(6)Cl-2 than in the kagome Heisenberg model, a likely signature of other interactions in the system.