ar X iv : c on d - m at / 9 61 21 81 v 1 1 9 D ec 1 99 6 MAGNETIC PROPERTIES OF THE 2 D t – t ′ – HUBBARD MODEL

The two–dimensional (2D) t–t’–Hubbard model is studied within the slave–boson (SB) theory. At half–filling, a paramagnetic to antiferromagnetic phase transition of first order at a finite critical interaction strength Uc(t /t) is found. The dependences on U/t and t/t of the sublattice magnetization and of the local magnetic moment are calculated. Our results reasonably agree with recent (Projector) Quantum Monte Carlo data. The SB ground–state phase diagram reveals a t–induced electron–hole asymmetry, and, depending on the ratio t/t, the antiferromagnetic or ferromagnetic phases are stable down to U = 0 at a critical hole doping.