Venkataiah G, Lakshmi Y Kalyana, Prasad V, Reddy P Venugopal
Department of Physics, Osmania University, Hyderabad 500007, India.
J Nanosci Nanotechnol. 2007 Jun;7(6):2000-4. doi: 10.1166/jnn.2007.757.
A systematic investigation of lanthanum-based manganite, La0.67Sr0.33MnO3, has been undertaken with a view to understand the influence of varying particle sizes on electrical transport properties. With a view to obtain materials with varying particle size, they were prepared by sol-gel route, sintering at four different temperatures. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD data has been analyzed by Rietveld refinement technique and it has been confirmed that the materials have rhombohedral crystal structure with R3c space group. Metal-insulator transition temperatures (Tp) were found to decrease continuously with decreasing particle size where as ferro to paramagnetic transition temperatures (Tc) are found to remain constant. The magnetoresistance (MR) values are found to increase with decreasing particle size. With a view to understand the conduction mechanism, the electrical resistivity data have been analyzed both in the ferromagnetic metallic (T < Tp) as well as high temperature paramagnetic insulating (T > Tp) regions.
为了了解不同粒径对电输运性质的影响，对镧基锰酸盐La0.67Sr0.33MnO3进行了系统研究。为了获得不同粒径的材料，通过溶胶-凝胶法在四个不同温度下烧结制备了这些材料。通过X射线衍射（XRD）和扫描电子显微镜（SEM）对样品进行了表征。利用Rietveld精修技术对XRD数据进行了分析，证实了材料具有R3c空间群的菱面体晶体结构。发现金属-绝缘体转变温度（Tp）随着粒径减小而持续降低，而铁磁-顺磁转变温度（Tc）保持不变。发现磁电阻（MR）值随着粒径减小而增加。为了理解传导机制，对铁磁金属（T < Tp）以及高温顺磁绝缘（T > Tp）区域的电阻率数据都进行了分析。
