MAGNETIC-PROPERTIES OF THE DOUBLE-EXCHANGE MODEL

We study the ferromagnetic (FM) Kondo lattice model in the strong-coup ling limit (the double-exchange (DE) model). The DE mechanism proposed by Zener to explain ferromagnetism is found to have unexpected proper ties when there is more than one itinerant electron. We End that, in g eneral, the many-body ground state of the DE model is not globally FM ordered (except for in special filled-shell cases). Furthermore, the l ow-energy excitations of this model are distinct from those in usual H eisenberg ferromagnets, which will result in unusual dynamic magnetic properties.