Thermal conductivity of silver doped lanthanum manganites between 10 and 300 K

Abstract

Thermal conductivity ( λ) of nanocrystalline La 1− x Ag x MnO 3 ( x=0.05, 0.15, 0.25, 0.3) pellets prepared by pyrophoric method is reported between 10 and 300 K. Magnitude of thermal conductivity has been found to be strongly influenced by monovalent (Ag) substitution at the La site. Silver doping in LaMnO 3 enhances T C of the system to ∼299 K. Qualitative nature of the temperature variation of thermal conductivity of the silver substituted lanthanum manganites remains closely similar to that for divalent doped systems. Our analysis demonstrates that in La 1− x Ag x MnO 3 also, the mechanism of heat conduction is predominantly by phonons. The contribution of the electronic part is only ∼1% of the total λ. The spin wave contribution is also estimated close to T C, which for all the samples lies within ∼2%. At temperatures below ∼100 K, the measured data have been analyzed using phonon relaxation time method and the strengths of the various phonon scattering processes have been estimated. Our analysis further suggests strong influence of phonon scattering by 2D like defects in the thermal conductivity of monovalent doped lanthanum manganites at low temperatures (<70 K) in the ferromagnetic region.