Impact of In~(3+) ion substitution on microstructural, magnetic and dielectric responses of nickel-cobalt spinel ferrite nanocrystals

摘要

In this article, indium ion-doped mixed nickel-cobalt ferrite nanoparticles with chemical composition N_(0.7)Co_(0.3)In_xFe_(2-x)O_4 (x = 0.00, 0.05, 0.10, 0.15 and 0.30) were synthesized using soft co-precipitation method. All prepared nanoferrites showed pure cubic spinel structure without containing any impurity phases as ensured by X-ray diffraction profiles. Mean diameters of nanocrystals were found within the range of 5 nm to 13 nm as estimated from Williamson-Hall (W-H) plots. Due to large size of In~(3+) ions, the compressive microstrain inside the nanocrystals became tensile in nature. Both the coercive field and saturation magnetization were reduced with increasing In~(3+) ion concentration in nickel-cobalt ferrite nanoparticles. Overall effective anisotropy was noticed to decrease with In~(3+) ion doping. This is due to the diamagnetic response of indium ions and weakening of magnetic interactions. Hopping of electrons between sub-lattice sites was the charge conduction process for all nanoferrites as confirmed by the AC conductivity measurement. Single semi-circular arc was observed in Cole-Cole plot for all samples which also revealed that the non-conductive grain boundaries was most effective in comparison to grains in dielectric responses. Decrement in the radius of semi-circles with respect to pristine sample also indicated the enhancement in DC conductivity with indium doping.