Study of the Structural, Electrical and Magnetic Properties of the ${\text{La}}_{0.67} {\text{Sr}}_{0.33 - x} {\text{Pb}}_{x} {\text{MnO}}_{3}$ Manganite Nanocrystalline Materials

Abstract

The manganite materials of ${\text{La}}_{0.67} {\text{Sr}}_{0.33} {\text{MnO}}_{3}$ family are of recent interest because of their high magnetic moment at room temperature and large Curie temperature which can be easily adjusted by the suitable substitution in the (La,Sr)-site. The interest in them is extended also because of the change in their electronic and magnetic properties with grain size reduction. The present paper contains the studies on the structural, electrical and magnetic properties of the manganite nanomaterials of ${\text{La}}_{0.67} {\text{Sr}}_{0.33 - x} {\text{Pb}}_{x} {\text{MnO}}_{3}$ ($x$ = 0, 0.05, 0.10, 0.15, 0.25, and 0.33) series. Refinement of the powder X-ray diffractograms reveals that all samples crystallize into a rhombohedral structure with the $R\overline{3} c$ space group. The lattice cell volume increases with the increase in $x$ upto $x = 0.15$, then decreases for higher $x$ values. The micrographs obtained using a field emission scanning electron microscope show that the grain size of these samples varies in the range of 30–50 nm. The resistivity curves exhibit a broad hump around the metal–insulator transition temperature, $T_{{{\text{MI}}}}$, which is extrinsic in behavior. From the studies of the field cooled magnetization, it is observed that the temperature of ferromagnetic ordering ($T_{{\text{C}}}$) falls in the range of 330.3–366.2 K. The results were explained in the framework of the theory of double exchange interaction. The field-dependent magnetization study shows ferromagnetic with very small coercive field and remanent magnetization of the samples at room temperature with reasonably large saturation magnetization. The present study reveals that the Pb-substitution could tune the physical properties of these materials according to their desired applications.