title: Cluster mean-field theory study of J1-J2 Heisenberg model on a square lattice.
abstract: We study the spin-1/2 J1-J2 Heisenberg model on a square lattice using the cluster mean-field theory. We find a rapid convergence of phase boundaries with increasing cluster size. By extrapolating the cluster size L to infinity, we obtain accurate phase boundaries J(c1)(2) ≈ 0.42 (between the Néel antiferromagnetic phase and non-magnetic phase), and J(c2)(2) ≈ 0.59 (between non-magnetic phase and the collinear antiferromagnetic phase). Our results support the second-order phase transition at J(c1)(2) and the first-order one at J(c2)(2). For the spin-anisotropic J1-J2 model, we present its finite temperature phase diagram and demonstrate that the non-magnetic state is unstable towards the first-order phase transition under intermediate spin anisotropy.
authors.affiliation: Department of Physics, Renmin University of China, 100872 Beijing, People's Republic of China.
authors.forename: Yong-Zhi
authors.initials: YZ
authors.lastname: Ren
authors.forename: Ning-Hua
authors.initials: NH
authors.lastname: Tong
authors.forename: Xin-Cheng
authors.initials: XC
authors.lastname: Xie
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D004735:Energy Transfer; D005296:Ferrous Compounds / Q000737:chemistry*; D060526:Magnetic Fields; D015233:Models, Statistical; D044367:Phase Transition; D011789:Quantum Theory; D013113:Spin Labels; D013696:Temperature
chemical_list: D005296:Ferrous Compounds; D013113:Spin Labels