The effect of Ni/Fe ratio on the physical properties of NiFe2O4 nanocomposites

Spinel ferrites nanoparticles were prepared using hydrothermal technique. The atomic ratio of Ni to Fe in the solution is ranged from 0 to 75% in order to investigate its effect on the structural, morphological and magnetic properties of the prepared spinel phases. The powder crystallographic structure was studied by means of x-ray diffraction (XRD). The morphology was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) observations. Vibrating sample magnetometer (VSM) was used to characterize the magnetic properties of powders. The XRD analysis reveals that the powders prepared with ratios Ni/Fe of 25 and 50% are pure nickel ferrite phase. However, at 75% ratio the powder is a mixture of hematite and mainly nickel hydroxide. The obtained nickel ferrites show narrow distribution of grain size which is reduced with increasing the Ni/Fe ratio; this variation is explained in terms of nucleation and grain growth. Nickel ferrite nanopowders exhibit a superparamagnetic behavior, due to their small size, and high magnetization saturation of 29.88 emu g−1. Thereafter, the prepared powders may found biomedical applications such as drug delivery.