Composite polaron mechanism for colossal magnetoresistance in perovskite manganites

The mechanism of carriers accompanied by spin-wave cloud and Jahn-Teller ph ononic cloud, called composite polaron, is proposed to explain the unusual transport and thermodynamic properties in perovskite manganites over all th e temperature and magnetic field range. It is shown that the energy bandwid th of composite polarons is strongly renormalized with the increases of tem perature and magnetic field, the bandwidth narrows with elevated temperatur e, while it broadens with increasing magnetic field. The resistivity of com posite polarons increases with elevated temperature strongly, reaches a max imum near the Curie temperature T-c, and decreases with the increase of mag netic field. The specific heat of composite polarons also exhibits a maximu m near T-c. These results agree with experiments in a broad temperature and magnetic field range, suggesting that composite polarons contribute to the unusual propel ties in manganites. (C) 1998 American Institute of Physics. [S0021-8979(98)45711-6].