STABILITY OF THE SATURATED FERROMAGNETIC STATE IN THE ONE-BAND HUBBARD-MODEL

We discuss the stability of the saturated ferromagnetic state of the one-band Hubbard model against a single spin flip in the limit of infinite on-site repulsion. We consider the case where the number of holes Nh, can be large but satisfies the condition NhlnN, in two dimensions, (NhN1/3 in three dimensions) where N is the number of spins. We show that the Nagaoka state is locally stable, except for certain small values of Nh for which there is an instability at long wavelengths. © 1990 The American Physical Society.