In this study, the effect of temperature parameter in order to optimize magnetic parameters of cobalt substituted nickel ferrite nanoparticles with composition, Ni1-xCoxFe2O4, where 0.0≤x≤1, synthesized using co-precipitation method has been investigated. Magnetic nanoferrites have attracted the attention of researchers due to their unique physical and chemical properties. In the meantime, soft nickel-cobalt ferrites with chemical structure of Ni-CoFe2O4 due to their high saturation magnetization, about 18.5 emu/g, in different such as magnetic sensors, magnetic storage tools, magnetic resonance imaging, wave absorbers, targeted drug delivery, inducers, etc. have been used. Suitable amounts of raw materials including iron, cobalt and nickel nitrates were dissolved in distilled water with appropriate stoichiometry ratios. The resulting solution was continuously heated under magnetic stirring in order to obtain precipitate. This precipitate dried in the oven and to achieve pure phase and spinel structure, calcinated in 600 and 1000℃. Microstructural studies on synthesized samples using X-ray diffraction (XRD) method showed that, in all samples the spinel structure of phases was formed. As annealing temperature increased, particle size increased. Morphology and particle size were measured using scanning electron microscopy (SEM). The obtained images showed that the average particle size with increasing cobalt did not have a clear order. The average sizes of nanoparticles in 600 ℃ and 1000 ℃ are estimated to be 13-19 nm and 28-36 nm, respectively. Fourier transform infrared spectroscopy (FTIR) was performed to confirm the placement of cations in octahedral and tetrahedral sites and ferrite formation. Magnetic properties were eva‎luated by vibrating sample magnetometer (VSM). The results of these measurements showed that with increasing cobalt amount, coercivity had a relatively increasing trend in two temperatures. Also, increasing the residual magnetization and saturation magnetization at two temperatures of 600 and 1000 °C by increasing the amount of cobalt was due to the replacement of nickel ion with cobalt ion, which increased the number of unpaired electrons in octahedral sites. By adding different amounts of cobalt, it has been concluded that nickel ferrite with concentration of 0.8 mol cobalt at 600 °C and nickel ferrite at 1 mol concentration at 1000 °C have an optimal amount of cobalt in order to achieve more desirable properties.

مهدي علي‌زاده

عباس بهرامي، رحمت الله عمادي