  The phase diagram of the Kondo lattice Hamiltonian with ferromagnetic Hund's
coupling in the limit where the spin of the localized $t_{2g}$ electrons is
classical is analyzed in one dimension as a function of temperature, electronic
density, and a direct antiferromagnetic coupling $J'$ between the localized
spins. Studying static and dynamical properties, a behavior that qualitatively
resembles experimental results for manganites occurs for $J'$ smaller than 0.11
in units of the $e_g$ hopping amplitude. In particular a coexistence of
ferromagnetic and antiferromagnetic excitations is observed at low-hole density
in agreement with neutron scattering experiments on
$\rm{La_{2-2x}Sr_{1+2x}Mn_2O_7}$ with$x=0.4$. This effect is caused by the
recently reported tendency to phase separation between hole-rich ferromagnetic
and hole-undoped antiferromagnetic domains in electronic models for manganites.
As $J'$ increases metal-insulator transitions are detected by monitoring the
optical conductivity and the density of states. The magnetic correlations
reveal the existence of spiral phases without long-range order but with fairly
large correlation lengths. Indications of charge ordering effects appear in the
analysis of charge correlations.
