Abstract
NiFe2O4, Al2O3 and their nanocomposites; (1-x) NiFe2O4 + (x) Al2O3, 0.0 <= x <= 1; were synthesized using the citrate- nitrate technique. The crystal structure was examined by X-ray diffraction, the microstructure was observed by transmission electron microscopy. The Curie temperature T-C grows until reaching more than 1100 K with increasing alumina content (x), while the saturation magnetization (M-s) decreased. The large improvement of room temperature resistivity which achieved two orders of magnitude from x = 0 to x = 70% was interpreted from the fact that the NiFe2O4 grains become electrically isolated and the conduction path is broken by the insulating Al2O3 nanoparticulates in the composite. The electrical properties of the nanocomposite could thus be tuned easily by adjusting the Al2O3 ratio to realize the targeted value of losses and resistivity at any temperature and frequency.