Interpretation of Thermal Conductivity in the Ferromagnetic Metallic Phase of La0.83Sr0.17MnO3 Manganites: Scattering of Phonons and Magnons

Abstract

The lattice contribution to the thermal conductivity (κph) is theoretically analyzed within the framework of Kubo model in La0.83Sr0.17MnO3 manganites. The theory is formulated when thermal conduction is limited by the scattering of phonons from defects, grain boundaries, charge carriers, and phonons. The lattice thermal conductivity dominates in La-Sr-MnO manganites and is artifact of strong phonon-impurity and -phonon scattering mechanism in the ferromagnetic metallic state. The electronic contribution to the thermal conductivity (κe) is estimated following Wiedemann-Franz law. This estimate sets an upper bound on κe, and in the vicinity of Curie temperature (Tc) is about 1% of total heat transfer of manganites. Another important contribution in the metallic phase should come from spin waves (κm). It is noticed that κm increases with a T2 dependence on the temperature. These channels for heat transfer are algebraically added and κtot develops a broad peak at about 120 K, before falling off at lower temperatures. The behaviour of the thermal conductivity in manganites is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between electron, magnon, and phonon contributions. The numerical analysis of heat transfer in the ferromagnetic metallic phase of manganites shows similar results as those revealed from experiments.