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)0.7Ba0.3MnO3 (x = 0.05 and 0.15). X-ray diffraction data demonstrate that both samples possess dual crystallographic phases: rhombohedral R3¯c 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 (χ−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 T3/2 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 (σ2). 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 magneto-transport properties in manganite systems. [Display omitted] •Quenched disorder destroys the martensitic transition.•Two metal–insulator transitions are detected in the electrical resistivity.•Griffiths singularity improve the temperature coefficient of resistance.•A shallow minimum has been observed at low temperature resistivity.