Microstructural properties, electrical behavior and low field magnetoresistance of (1−x)La0.67Sr0.33MnO3 (LSMO)+(x)Ni0.5Zn0.5Fe2O4 (NZFO) composites

Abstract

Abstract The composites with composition of (1−x)La0.67Sr0.33MnO3 (LSMO)+(x)Ni0.5Zn0.5Fe2O4 (NZFO) with x=0.0 (S1), 0.04 (S2), 0.07 (S3), 0.10 (S4), 0.30 (S5) and 1.0 (S6) were synthesized by solid-state reaction route. Structural study using Rietveld refinement of X-ray diffraction (XRD) pattern indicates a rhombohedrally-distorted structure (space group R3c) for LSMO phase while to that NZFO compound crystallizes in cubic structure (space group Fd3m). XRD patterns and microstructural analysis show that LSMO and NZFO phase exists independently in Ni0.5Zn0.5Fe2O4 doped composites. The transport properties of the compositions x=0.0, x=0.04, and x=0.07 showed that NZFO phase improves the resistivity and shifts the metal–insulator transition temperature TMI towards lower temperature. The magnetoresistance (MR) of composite samples with x=0.04 and x=0.07 decreases monotonously from 200 to 300 K in a magnetic field of 8 T. At lower temperatures (~5 K), a sharp drop of negative MR at low fields (H 1 T) where MR is almost linear with applied magnetic field. Temperature dependence of resistivity for composites samples with x=0.04 and x=0.07 has been best fitted by small Polaron hopping (SPH) and variable range hopping models (VRH).