Zinc-substituted cobalt ferrite nanoparticles with the general formula of ZnxCo1−xFe2O4 (x = 0.0, 0.2, 0.4, 0.5 and 0.6) were synthesized via co-precipitation. X-ray diffraction (XRD) studies revealed that the strain created in the structures increased by adding zinc to the compositions. The calculated results from XRD data using Rietveld refinement indicated that the bond length decreases in the octahedral position and increases in the tetrahedral space with increasing zinc concentration in the composition. Morphology of the samples investigated by field emission scanning electron microscopy showed the formation of nearly spherical particles. Saturation magnetization (MS) of the synthesized samples showed an increasing trend up to x = 0.4, and then a decreasing behavior. The coercive field (HC) value was reduced from 1600 Oe for the zinc-free sample to 150 Oe for the Zn0.4Co0.6Fe2O4 composition. The ratio of remanence magnetization (Mr) to MS (Mr/Ms) in the zinc-doped samples was much lower than in the zinc-free sample, which is a sign of easy magnetic change after removal of the external magnetic field
