A study of the t-t'-U model in the antiferromagnetic phase by means of the COM is reported in Ref. . In particular the following properties have been computed:
The COM results have been analyzed in relation with the ones obtained by:
We provided simultaneously a fully self-consistent treatment of the paramagnetic and the antiferromagnetic phase. Near half filling the critical value of the Coulomb repulsion as a function of and the temperature dependence of the magnetization and internal energy have been studied. turns out to be significantly larger than what obtained by renormalization group techniques [88,89]. This might be due to the fact, that the latter is valid only in the weak coupling limit, whereas COM provides a good approximation for any value of the interaction. The band structure shows the opening of a gap at the transition line between the paramagnetic and the antiferromagnetic phase. With decreasing magnetization the energy increases and reaches the paramagnetic value at vanishing magnetization.