الفهرس 
LITERATURE SURVEYOnly 14 pages are availabe for public view
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Abstract
Polycrystalline NiFe2O4 and Al2O3 were prepared by the citrate-nitrate auto combustion method. Nanocomposites were prepared according to (1-x) (NiFe2O4)+(x) (Al2O3): x=10%, 30%,50%,70% and 90% weight percent. The samples were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscope ,energy dispersive X-ray, FTIR and vibrating sample magnetometer. saturation magnetization (MS) and mean grain size decrease with the increase of Al2O3 concentration while the Curie temperature increase with increasing Al2O3 due to different magnetic mechanisms. High temperature dependent of dielectric constant of the composites with different Al2O3 ratio shows usual dielectric dispersion behavior, which may be attributed to the Maxwell- Wagner type interfacial polarization. As x is increased, the enhancement of room temperature resistivity results from the fact that the NiFe2O4 grains become isolated electrically and the conduction network is broken by the insulating Al2O3 concentration in the composite and the intrinsic Verwey transition which is usually present in NiFe2O4 is dominated by grain boundaries or insulating Al2O3.