Magnetic Susceptibility of the Kagome AntiferromagnetZnCu3(OH)6Cl2

We analyze the experimental data for the magnetic susceptibility of the material ${\mathrm{ZnCu}}_3(\mathrm{OH}{)}_6{\mathrm{Cl}}_2$ in terms of the Kagome Lattice Heisenberg model (KLHM), discussing possible role of impurity spins, dilution, exchange anisotropy, and both out-of-plane and in-plane Dzyloshinski-Moriya (DM) anisotropies, with explicit theoretical calculations using the numerical linked cluster method and exact diagonalization. The high-temperature experimental data are well described by the pure Heisenberg model with $J=170\mathrm{K}$. We show that the sudden upturn in the susceptibility around $T=75\mathrm{K}$ is due to DM interactions. We also observe that at intermediate temperatures, below $T=J$, our calculated susceptibility for KLHM fits well with a power law $T^{-0.25}$.