MAGNETIC EXCITATION IN THE HUBBARD-HIRSCH MODEL

Based on the Hubbard-Hirsch model, we studied the dynamical susceptibi lity and spin excitation of an itinerant-electron system within the ra ndom-phase approximation by using a Green's-function technique. It is shown that the two-center matrix elements in the Hubbard-Hirsch model not only change the dynamic property of the susceptibility, but also w iden the gap between two spin subbands, which suppresses the electron- hole single excitations. In contrast, the region of collective excitat ions of the spin becomes larger.