Study on Conductive and Magnetic Properties of Ag-Doped La 0.67 Sr 0.33 MnO 3

Abstract

Rare-earth doped manganese oxide La 0.67 Sr 0.33 MnO 3 (LSMO) has broad application prospects in the field of spin electronics, which has the paramagnetic-ferromagnetic transition temperature (T c ) above room temperature. Recent research shows that Ag-doping has effective improvements of grain size and conductivity of LSMO for improving the colossal magnetoresistance effect (CMR). In this paper, sol-gel method was used to prepare La 0.67 Sr 0.33 MnO 3 : Agx（x=0, 0.5 mol%） polycrystalline powder. By using X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS) technologies, the microstructure, crystalline phase structure, resistivity, magnetic properties, Ag and Mn valence states of LSMO were tested before and after Ag doping, respectively. The analysis shows that some Ag atoms exist at the grain boundary of LSMO in the form of element to enhance the conductivity; other Ag atoms go into the crystal lattice replacing A site La 3+ in the perovskite structure ABO3, which obtains a small amount of La 2 O 3 hybrid phase in LSMO and decreases the ratio of Mn 3+ /Mn 4+ . Ag doping weakens the double exchange effect and the magnetic property of LSMO. The substitution of La with Ag also makes minority spinon band of LSMO slightly reduced, which can weakly decrease the conductivity of LSMO.