Ferromagnetism in the strong-coupling regime of the one-dimensional Kondo-lattice model

Abstract
The ground state of the one-dimensional Kondo lattice model is examined in the strong-coupling regime. An effective Hamiltonian is developed to describe low-energy processes. This leads to a ferromagnetic ground state in this regime for all conduction electron densities. The spin excitations are those of a squeezed spin chain with ferromagnetic Heisenberg exchange coupling. In addition there are quasiparticle excitations, which are discussed in detail only for the case of half filling.