Anomalous spin susceptibility and magnetic polaron formation in the double-exchange systems

The magnetic susceptibility and spin-spin correlation of the double-exchange model for doped manganites are investigated through the Monte Carlo calculations on the three-dimensional lattice model. Deviations of the susceptibility from the Curie-Weiss behavior above the ferromagnetic ordering temperature $T_c$ seem to indicate a formation of local ferromagnetic clusters in the vicinity of $T_c,$ which is consistent with recent electron paramagnetic resonance experiments for ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}{\mathrm{MnO}}_3.$ A further analysis of the spin-spin correlations show the ferromagnetic cluster size to be three-to-four lattice spacings, suggesting that the charge carriers may form magnetic polarons.