FERROMAGNETISM IN THE ONE-DIMENSIONAL KONDO-LATTICE MODEL

We investigate the incompletely saturated ferromagnetic phase which oc curs at strong coupling in the partially filled one-dimensional (1D) K ondo lattice model. The double-exchange interaction responsible for th e ferromagnetic ordering is absent in dilute Kondo systems, and is a m issing element in nearly all theoretical treatments of the model. We d iscuss how double-exchange arises in the system, even though the Kondo coupling is antiferromagnetic, and show that at strong coupling it fa vors an alignment of the spins of unpaired localized moments. A ground -stale phase diagram for the localized moments is given, with double-e xchange interactions included, and is in complete qualitative agreemen t with numerical simulations. (C) 1998 Elsevier Science B.V. All right s reserved.