METAMAGNETISM IN THE 2-DIMENSIONAL HUBBARD-MODEL WITH EASY-AXIS

Although the Hubbard model is widely investigated, there are surprisin gly few attempts to study the behavior of such a model in an external magnetic field. Using the projector quantum Monte Carlo technique, we show that the Hubbard model with an easy axis exhibits metamagnetic be havior if an external field is turned on. For the case of intermediate correlations strength U, we observe a smooth transition from an antif erromagnetic regime to a paramagnetic phase. While the staggered magne tization will decrease linearly up to a critical field B-c, uniform ma gnetization develops only for fields higher than B-c. [S0163-1829(97)5 0840-X].