REENTRANT BEHAVIOR IN A HIGHLY ANISOTROPIC SYSTEM

The critical behaviour of a spin-I system made up of weakly coupled ch ains is analyzed by the linear chain approximation, which first uses t he transfer matrix method to find the exact solution of the linear cha in and then the Bogolubov variational principle to determine the free energy of the overall system. The model Hamiltonian is a BEG-like with dipolar and quadrupolar couplings and a single-ion anisotropy term. T he system is investigated for several ratios of interchain and intrach ain interaction terms. A detailed analysis of the role of the intercha in terms in the reentrant phenomenon is performed.