Preparation And Physical Properties Of La_1-xSb_xMnO₃Perovskite Material

The doped pervoskite manganites have attracted considerable attention because oftheir colossal magnetoresistance （CMR） effect in fundamental physics and theirpotential applications such as magnetic storage and magnetic sensors during lasttwenty years. The main content of this thesis is summarized as follows:1. The history and the future for CMR mangnities is reviewed. The structure,magnetic and electrical transport properties of the CMR mangnities is introduced. Theunderlying physics mechanism including small polaron, double exchange, and phaseseparation models is introduced, too.2. La_1-xSb_xMnO₃bulks were synthesized successfully by solid state reaction.X-ray diffraction results indicate they had single-phase orthorhombic symmetrystructure. The infrared spectra for the sample were obtained using Fourier Infraredspectumeter. The absorption peaks around420cm^-1and610cm^-1were found. Bothpeaks come from infrared active vibrating modes ν3and ν4of MnO6octahedron inperovskite structure. Gauss function was used to fit the spectra. As a result, the peaksplit into several absorption peaks. The stretch-mode absorption peak near610cm^-1split into two peaks with the gap about66cm^-1, which is explained by phaseseparation in La_1-xSb_xMnO₃compounds.3. La_0.9Sb_0.1MnO₃（LSMO） thin films were deposited on single-crystal LaAlO3（001） substrates by pulsed laser deposition technique. The films have a perovskitesingle-phase structure from X-ray diffraction pattern. The electrical transport andmagnetic properties have been investigated for La₀.9Sb₀.1MnO₃thin films withthickness300nm. The result indicates that the film perform the colossalmagnetoresistance （CMR） effect with the maximum magnetoresistance （MR） ratio of63%at temperature of190K and field of2.3T.