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

The composites with composition of (1− x )La 0.67 Sr 0.33 MnO 3 (LSMO)+( x )Ni 0.5 Zn 0.5 Fe 2 O 4 (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 R 3 c ) for LSMO phase while to that NZFO compound crystallizes in cubic structure (space group Fd 3 m ). XRD patterns and microstructural analysis show that LSMO and NZFO phase exists independently in Ni 0.5 Zn 0.5 Fe 2 O 4 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 T MI 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) has been observed followed by a slower varying MR at a comparatively high-field regime ( 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). [ABSTRACT FROM AUTHOR]