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

The magnetic susceptibility and spin-spin correlation of the double-exchang e model for doped manganites are investigated through the Monte Carlo calcu lations on the three-dimensional lattice model. Deviations of the susceptib ility from the Curie-Weiss behavior above the ferromagnetic ordering temper ature T-c seem to indicate a formation of local ferromagnetic clusters in t he vicinity of T-c which is consistent with recent electron paramagnetic re sonance experiments for La2/3Ca1/3MnO3. A further analysis of the spin-spin correlations show the ferromagnetic cluster size to be three-to-four latti ce spacings, suggesting that the charge carriers may form magnetic polarons .