Magnetic properties of an exactly solvable antiferromagnetic Ising–Heisenberg model on the decorated triangular lattice

Abstract Mixed-spin Ising–Heisenberg model on the decorated triangular lattice is studied by the use of an exact star–triangle map. Within this approach, exact results for the ground-state and finite-temperature behaviour of the antiferromagnetic version of the model are obtained. A particular attention is laid on the effect of exchange anisotropy and next-nearest-neighbour interaction on magnetic behaviour of the system. It was found that the competitive effect between the nearest-neighbour Heisenberg-type, nearest- and next-nearest-neighbour Ising-type interaction, respectively, leads to a remarkable spin frustration in the system. In addition, very weak next-nearest-neighbouring coupling is responsible for an interesting reentrant critical behaviour with two or three consecutive critical points.