Low-temperature thermodynamic properties of a random anisotropic antiferromagnetic chain

The low-temperature thermodynamic properties of a spin- one-dimensional random anisotropic (Heisenberg-Ising) antiferromagnet described by the Hamiltonian H=i^J₈ (ₗ^iₗ^i+1+ₘ^iₘ^i+1+ₙ^iₙ^i+1) are studied as a function of disorder and anisotropy. The J₈>~0 are independent random variables obeying a probability distribution P (J), and 01) the susceptibility shows an approximate power-law divergence for small anisotropy but goes eventually to zero as T0. Possible relevance of these results to recent experiments on Qn (TCNQ) ₂ is discussed.