Local lattice distortions and thermal transport in perovskite manganites

Abstract

Measurements of thermal conductivity versus temperature and magnetic field are reported for perovskite manganites that exhibit ferromagnetic (FM), charge-ordering (CO), antiferromagnetic, and/or structural phase transitions. The data reveal a dominant lattice contribution to the heat conductivity with $\ensuremath{\kappa}\ensuremath{\sim}1\ensuremath{-}2$ W/mK near room temperature. The rather low values, implying a phonon mean free path on the order of a lattice spacing, are shown to correlate with static local distortions of the ${\mathrm{MnO}}_{6}$ octahedra. Modifications of the local structure are responsible for abrupt anomalies in the zero-field \ensuremath{\kappa} at the FM, CO, and structural transitions, and for colossal magnetothermal resistance near the FM transition.