Study of structure, transport, paramagnetic and ferromagnetic properties of La0.8Sr0.2Mn1−xZnxO3 perovskite manganite

Abstract

La0.8Sr0.2Mn1−xZnxO3 perovskite manganite with x = 0, 0.01, 0.03, 0.05, 0.1, 0.15, 0.3, 0.5 and 0.75 has been prepared by the solid state reaction and investigated by structural, transport and magnetic measurements. The structural characterization of the samples has been done by x-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The x-ray powder diffraction results indicate a single phase for 0 < x < 0.5, confirming that zinc is incorporated on the Mn site. The lattice parameters (a, b, c) of this orthorhombic system increase with increasing zinc concentration in the system. According to the SEM images, the grain size of the materials with x > 0.1 decreases with increasing zinc doping levels. The transport measurements show that the insulator-to-metal transition temperature, Tc, decreases with increasing zinc substitution on the Mn site, and the resistivity increases. The Tc variations agree with the magnetic measurement data for x < 0.3. The compound changes from ferromagnetic to paramagnetic for x > 0.3. The possible mechanism behind the effects of zinc doping into the La0.8Sr0.2Mn1−xZnxO3 system involves degradation of the double exchange between Mn3+–O–Mn4+ in this compound.