Journal of Physics C Solid State Physics
On the critical behaviour of an Ising system with lattice coupling
J. Oitmaa, Michael N. Barber
Abstract
The Hamiltonian H=-J 2 Sigma (ij) sigma i sigma j -(J 4 /N) Sigma (ij)(kl) sigma i sigma j sigma k sigma l where the first term is a nearest-neighbour pair interaction and the second term is an infinite-range pair-pair interaction, is proposed as a model of an Ising magnet with lattice coupling. The free energy is reduced to that of a rigid Ising model on the same lattice but with a modified pair interaction. In two and three dimensions, the phase transition is found to be first order for all J 4 . The relationship between this result and recent renormalization group calculations is discussed.