Structural and magnetotransport properties of (La, Pr)-Ba manganites

We report on the structural, magnetic and transport properties of the Pr-doped manganite (La1-xPrx)(0.7)Ba0.3MnO3 (x = 0.05 and 0.15). X-ray diffraction data demonstrate that both samples possess dual crystallographic phases: rhombohedral R (3) over barc and orthorhombic Pnma. This is due to the martensitic phase transition inherent to the pristine La0.7Ba0.3MnO3 sample, whose impact is seen as a second metal-insulator (MI) transition below the ordered temperature in electric measurements. Griffiths phase (GP)-like behavior in the inverse magnetic susceptibility (chi(-1) (T)) was observed only for Pr-15%. The origin of the Griffiths singularity could be understood in terms of the competing accommodation strain arising from martensite-like phase transition and quenched disorder. Interestingly, GP cannot be considered as a precursor for the magnetoresistance (MR), but can be essential for improving the temperature coefficient of resistance (TCR). At low temperature, the magnetization follows the Bloch's T-3/(2) law, while the resistivity shows a shallow minimum in both samples. Our work reveals that, at low temperature, the influence of the magnetic contribution of Pr3+ becomes relevant against the quenched disorder (sigma(2)). These findings suggest that quenched disorder, strain field, and the coupling between rare-earth and Mn3-/Mn4- sublattice are important factors in determining the structural and magnetotransport properties in manganite systems. (C) 2019 Elsevier B.V. All rights reserved.