Effect of Sr-Doping on Structural and Magnetic Properties of La1−xSrxMnO3 Nanoparticles

Abstract

Polycrystalline La[Formula: see text]SrxMnO3 ([Formula: see text]–0.4) lanthanum strontium manganese oxide (LSMO), nanoparticles exhibit interesting size-dependent structural and magnetic properties. LSMO nanoparticles have attracted considerable attention in recent years because of their tunable magnetic properties like intrinsic and extrinsic colossal magnetoresistance, single domain superparamagnetic structure with near room temperature Curie point ([Formula: see text]). They find interesting applications in catalysis, biomedicine and data storage. Properties of LSMO nanoparticles are strongly correlated to extent of Sr-doping at La-site, their particle size and the extent to which different crystallographic phases (rhombohedral/orthorhombic) appear. A major aim of this study is to understand the effect of Sr-doping on the structural and magnetic properties of LSMO nanoparticles synthesized via the sol–gel auto combustion route. Structural and magnetic properties were investigated by powder X-ray diffraction coupled with Rietveld refinement and vibrating sample magnetometer, respectively. Rietveld refinement of diffractograms revealed that irrespective of Sr-doping, LSMO nanoparticles were crystallized in rhombohedral ([Formula: see text]) and orthorhombic (Pbnm) mixed phases. The rhombohedral phase appears to be the dominant crystallographic phase. VSM study revealed that irrespective of Sr-doping LSMO nanoparticles exhibit soft ferromagnetic behavior. With the increase in Sr-doping, saturation magnetization ([Formula: see text]) of LSMO nanoparticles increases, while their Curie temperature remains constant at [Formula: see text][Formula: see text]K. To establish the correlation between structural and magnetic properties of LSMO nanoparticles, [Formula: see text]–[Formula: see text] curves were fitted with modified Langevin function. It was observed that with an increase in Sr-doping, magnetic domain size, polydispersity and saturation magnetization increase. This increase is attributed to the corresponding increase in the rhombohedral phase fraction of LSMO nanoparticles. Thus, through Sr-doping, the magnetic properties of LSMO nanoparticles can be tuned by controlling their crystallographic phase fractions.