  We investigate the two- and three-dimensional ferromagnetic Kondo lattice
model by unbiased Monte Carlo simulations. A phase diagram for the
two-dimensional model is presented, in which the stability of magnetic order
and ferromagnetic polarons is examined with respect to the antiferromagnetic
superexchange J' and temperature. The Monte Carlo simulations reveal that J' >
0.02 strengthens individual polarons while small J' < 0.02 favors larger
clusters and phase separation except for small doping. Lowering the temperature
stabilizes ferromagnetic polarons for realistic J' > 0.01, while phase
separation is only favored for very small J' < 0.01. Our Monte Carlo
simulations show that low temperatures can lead to diagonal or vertical stripes
depending on J'.
  Simulations for three-dimensional systems yield ferromagnetic polarons, which
form a `polaron lattice' at higher doping levels 0.2 < x < 0.23, when
independent polarons do no longer fit into the system. No tendency to phase
separation is observed in three dimensions.
