  The electronic structure of perovskite manganese oxides is investigated in
terms of a Kondo lattice model with ferromagnetic Hund coupling and
antiferromagnetic exchange between $t_{2g}$-spins using a finite temperature
diagonalization technique. Results for the dynamic structure factor are
consistent with recent neutron scattering experiments for the bilayer manganite
La$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$ . The susceptibility shows Curie-Weiss
behaviour and is used to derive a phase diagram. In the paramagnetic phase
carriers are characterized as ferromagnetic polarons in an antiferromagnetic
spin liquid.
