Antiferromagnetism in the 2D Hubbard model: Phase transition and local quantities

We present a first study of the antiferromagnetic state in the 2D U-t-t′ model at finite temperatures by the composite operator method, providing simultaneously a fully self-consistent treatment of the paramagnetic and the AF phase. Near half-filling the critical value of the Coulomb repulsion as a function of t′ and the temperature dependence of the magnetization and of the internal energy per site have been studied. © 2000 Elsevier Science B.V. All rights reserved.