مطالعه اثر دمای بازپخت بر ویژگی های ساختاری و مغناطیسی نانوذرات فریت Ni0.3Fe0.7Fe2O4

In this investigation nickel-cadmium ferrite nanoparticle with stoichiometric composition of Ni0.3Cd0.7Fe2O4 was synthesized by Sol-gel auto- combustion method. In order to study the effect of particle size on physical properties of samples, the powder samples was annealed at temperatures 350, 400, 450 and 500 ○ C for 3h. Structural, morphological and magnetic properties of samples were analyzed using X- ray diffraction (XRD), field emission scanning electron microscope (FESEM), vibrating sample magnetometer (VSM) and ac susceptibility. XRD data revealed spinel mono-phase formation and crystallite size was estimated in the range of 17- 35 nm, using sherrer’s equation which also confirmed by FESEM. The VSM results indicate that magnetization increases by increasing particle size. Using the results of ac susceptibility measurements and analysis by the Neel- Brown, Vogel-Fulcher and critical slowing down methods, indicates that the samples annealed at temperatures of 350  and    400    ○ C are super-paramagnet at room temperature and have super-spin glass behavior at low temperatures.