Double-exchange magnets: Spin dynamics in the paramagnetic phase

The electronic structure of perovskite manganese oxides is investigated in terms of a Kondo lattice model with ferromagnetic Hund coupling and antifer romagnetic exchange between t(2g) spins using a finite temperature diagonal ization technique. Results for the dynamic structure factor are consistent with recent neutron-scattering experiments for the bilayer manganite La1.2S r1.8Mn2O7. The susceptibility shows Curie-Weiss behavior and is used to der ive a phase diagram. In the paramagnetic phase with pronounced antiferromag netic fluctuations charge carriers form ferromagnetic polarons.