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-J₁′-J₂ 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 Néel and stripe states, as compared with all previous results for the corresponding spin-1/2 case. However, we find a quantum tricritical point at J₁′/J₁≈0. 66±0.03, J₂/J₁≈0.35±0.02, where a line of second-order phase transitions between the quasi-classical Néel and stripe-ordered phases (for J₁′/J₁≲0.66) meets a line of first-order phase transitions between the same two states (for J₁′/J₁≳0.66).