Chemical disorder induced positive magnetoimpedance in La0.7Pb0.3Mn0.35Fe0.65O3−δ and La0.7Pb0.3Mn0.3Fe0.7O3−δ manganites

Abstract

We report structural, magnetic and magnetoimpedance properties of La0.7Pb0.3Mn0.35Fe0.65O3−δ and La0.7Pb0.3Mn0.3Fe0.7O3−δ manganites. Bulk samples were prepared by solid state method. Rietveld refinement of the X-ray diffraction pattern shows the crystallization of these samples in trigonal crystal system. Fe doping at Mn site in La0.7Pb0.3MnO3 increases the lattice parameters and induces oxygen non stoichiometry in the lattice of La0.7Pb0.3Mn0.35Fe0.65O3−δ and La0.7Pb0.3Mn0.3Fe0.7O3−δ. La0.7Pb0.3Mn0.3Fe0.7O3−δ composition shows ∼180% positive magnetoimpedance at 1 Tesla magnetic field while La0.7Pb0.3Mn0.35Fe0.65O3−δ shows ∼75% positive magnetoimpedance at 320 K. Magnetization versus applied magnetic field measurement curves show the magnetic moment of La0.7Pb0.3Mn0.35Fe0.65O3−δ and La0.7Pb0.3Mn0.3Fe0.7O3−δ do not saturate up to 2 tesla magnetic field at 300 K. Fe+3 doping at Mn site in these manganites created chemically modified phase separated systems. Huge positive magnetoimpedance in 65% and 70% Fe doped manganites originated by maxwell wagner effect due to the chemical disorder induced phase separated states and dominated coulombic interactions.