Ferromagnetic polarons in manganites

Using the Lanczos method in linear chains we study the double exchange mode l in the low concentration limit, including an antiferromagnetic super-exch ange K. In the strong-coupling limit we find that the ground state contains ferromagnetic polarons whose length is very sensitive to the value of Kit. We investigate the dispersion relation, the trapping by impurities, and th e interaction between these polarons. As the overlap between polarons incre ases, by decreasing Kit, the effective interaction between them changes fro m antiferromagnetic to ferromagnetic. The scaling to the thermodynamic limi t suggests an attractive interaction in the strong-coupling regime (J(h)>t) and no binding in the weak limit (J(h)similar or equal tot).