LAUSR

Abstract This report presents the structural, magnetoresistance, electrical and thermal transport properties of Aluminium substituted La 0.7 Ba 0.3 Mn 1−x Al x O 3 (0 ≤ x ≤ 0.15) compounds synthesized by solid state reaction method. To obtain crystallographic parameters, the X-ray diffraction patterns are fitted in R-3c space group with Rietveld refinement method. The resistivity and magneto-transport measurements are performed using standard four-probe assembly with and without magnetic fields. The peak resistivity ρ peak is noted at Metal-Insulator Transition temperature ( T MI ) and lowering in T MI is observed for higher concentrations of Al 3+ . The resistivity data have been analyzed in two parts. Firstly, in the metallic region below T MI the resistivity data is fitted with three degree polynomial. Secondly, in the semiconducting region above T MI data have been fitted with Variable Range Hopping (VRH) and Small Polaron Hopping (SPH) models. The Seebeck coefficients found to be positive throughout the temperature range (10 K–300 K) with holes as dominating charge carriers. Similar to the resistivity profile, in metallic region the thermo-power is explained with qualitative model based on diffusion, magnon-drag, phonon-drag and spin fluctuation contributions whereas the semiconducting region is explained with small polaron hopping model.