Low-density approach to the Kondo-lattice model

We propose an approach to the (ferromagnetic) Kondo-lattice model in the low-density region, where the model is thought to give a reasonable framework for manganites with perovskite structure exhibiting the colossal magnetoresistance effect. Results for the temp erature- dependent quasiparticle density of states are presented. Typical features can be interpreted in terms of elementary spin-exchange processes between itinerant conduction electrons and localized moments. The approach is exact in the zero-bandwidth limit for all temperatures and at T=0 for arbitrary bandwidths, fulfills exact high-energy expansions, and reproduces correctly second-order perturbation theory in the exchange coupling.