On the anisotropic Heisenberg chain

High-temperature expansions are derived for the specific heat and the _χzz element of the susceptibility tensor for a linear chain of spins $\text{1}\text{2}$ with anisotropic nearest-neighbour interactions. (The coupling constants J₁, J₂ and J₃ are chosen to be different.) Use is made of exact results of the XY model, a first-order perturbation calculation in J₃, a high-temperature expansion for the transverse susceptibility _χxx of the anisotropic XY model and the high-temperature expansion for the isotropic Heisenberg chain. Some characteristic features of deviations from the case of axial symmetry in the coupling constants are discussed.