Effect of Sr-Doping Concentration on Structure and Phase-Separation between Ferromagnetic and Paramagnetic Phases in Lanthanum Manganite Oxide

摘要

The perovskite La1-xSrxMnO3 (LSMO) nanocrystalline compounds with the doping concentration x in the range of 0.2～0.5 have been synthesized by combustion method using the pair of citric acid and ethylene glycol as a burning fuel.It was found that the sintering temperatures at which the compounds began forming the single-phase of LSMO increased from 900 °C up to 1200 °C corresponding to the increasing of Sr-doping content.X-ray pattern investigations presented the crystalline sizes of all samples sintered at 1200 °C evidently reduced from 77.7 nm to 18.9 nm as the doping concentration x increases.The effects of Sr-doping levels on Mn4+/Mn3+ ratio as well as on their electrical resistivity are also studied by X-ray photoelectron spectroscopy and four-point probes method,respectively.By using a resistive approximation model,the role of the Sr-doping with respect to the phase-separation between ferromagnetic and paramagnetic phases of these compounds is discussed.