Kagome lattice antiferromagnets and Dzyaloshinsky-Moriya interactions

We study the consequences of in-plane (Dₚ) and out-of-plane (Dz) Dzyaloshinsky-Moriya (DM) interactions on the thermodynamic properties of spin-1/2 Heisenberg model on the kagome lattice using numerical linked cluster expansions and exact diagonalization and contrast them with those of other perturbations such as exchange anisotropy and dilution. We find that different combinations of the DM anisotropies lead to a wide variety of thermodynamic behavior, which are quite distinct from those of most other perturbations. We argue that the sudden upturn seen experimentally in the susceptibility of the material ZnCu₃(OH)₆Cl₂ can be understood in terms of Dzyaloshinsky-Moriya anisotropies with Dₚ>Dz. We also show that the measured specific heat of the material puts further constraints on the allowed DM parameters.