Magnetic properties of the 2D 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 U_c(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. 
U. Trapper (a,b), H. Fehske (b) and D. Ihle (a) ((a) Institut f"ur   Theoretische Physik, Universit"at Leipzig (b) Physikali...