In this thesis, we report on the fabrication and the characterization of La 0.85 Ba 0.15 MnO 3 (LBMO) nano crystal. The samples have been prepared y sol-gel and new solid state method. Short time ball milling and non aqueous process are the advantage of this method. In the first part of this project, the effect of crystallite size on structural and magnetic properties of La 0.85 Ba 0.15 MnO 3 powders have been investigated. The samples have been characterized using X-ray diffraction and the average crystallite size of samples have been estimated by Scherrer formula. The structural parameters and space groups have been obtained by FULLPROF soft ware, Rietveld refinement. It shows that all the samples have Rombuhedral structure. FE-SEM and TEM images have shown that, the magnitude of grain size are in range of nanometer. Susceptibility and transition temperature have been decreased by lowering of crystallite size. The dynamic properties of sample has been prepared in temperature 620 o C with new method, has been investigated by ac susceptibility for superparamagnetism. Frequency dependence of blocking temperature has been well described by Vogel-Fulcher law. The temperature dependence of the real and imaginary parts of susceptibility for a sample, which as prepared by sol-gel method in temperature 1350 o C, and revealed unusual and interesting features which are associated with the domain walls and the effect of grain boundaries on their movements. In the second part, the effect of sintering temperature on structural, magnetic and electrical properties of La 0.85 Ba 0.15 MnO 3 have been investigated. The structural parameters and space groups have been obtained by FULLPROF soft ware, Rietveld refinement. It shows that all samples have same structure as powder samples. Magnetic susceptibility measurement showed that, the susceptibility increases with increasing sintering temperature. Magnetic susceptibility of bulk sample, prepared at temperature 1350 o C with sol-gel method, has been compared with powder sample of this method. The results showed that in bulk sample the anomaly disappeared. In order to study the traort properties of the samples temperature dependence of resistance have been measured. Insulator behavior has been disappeared with increasing sintering temperature and metal-insulator transition temperature has been observed. Samples resistance has decreased by increasing sintering temperature. Kay words: Nano manganite, Crystallite size, AC susceptibility, Superparamagnetic, Sintering temperature,
