Antiferromagnetic Correlation under the External Magnetic Field in the   Hubbard Model
  By deriving a generalized Harper's equation, we investigate the effects of temperature $T$ and hole doping $\d$ on antiferromagnetically correlated electrons under the influence of an applied magnetic field. We obtain a phase diagram in a $T$-$\d$ plane for staggered magnetization under the external field. We find that away from half filling the maximum values of staggered magnetization occur with rapid convergence to a finite temperature constant near half filling. We discover the reentrant behavior of the staggered magnetization in the presence of the magnetic field. 
S. P. Hong, H. Doh, and S. H. Suck Salk (Pohang University of Science   & Technology, Korea)