The quantum J1-J1′-J2 spin-1 Heisenberg model:: Influence of the interchain coupling on the ground-state magnetic ordering in 2D

We study the phase diagram of the isotropic J1-J(1)'-J(2) Heisenberg model for spin-1 particles on an anisotropic square lattice, using the coupled- cluster method. We find no evidence for an intermediate phase between the Neel and stripe states, as compared with all previous results for the corresponding spin-1/2 case. However, we find a quantum tricritical point at J(1)'/J(1) approximate to 0.66 +/- 0.03, J(2)/J(1) approximate to 0.35 +/- 0.02, where a line of second-order phase transitions between the quasi-classical Neel and stripe-ordered phases (for J(1)'/J(1) less than or similar to 0.66) meets a line of first-order phase transitions between the same two states (for J(1)'/J(1) greater than or similar to 0.66). Copyright (C) EPLA, 2008.