Carvalho, D.C.; Castro, L.M.; Plascak, J.A. - In: Physica A: Statistical Mechanics and its Applications 391 (2012) 4, pp. 1149-1157
The variational approach based on the Bogoliubov inequality for the free energy is used to study the three-dimensional anisotropic Heisenberg XXZ model with a crystal field. The magnetization and the phase diagrams are obtained as a function of the parameters of the Hamiltonian. Limiting cases,...