Study of magnetic and structural properties of ferrofluids based on cobalt-zinc ferrite nanoparticles

► Co(1−x)ZnxFe2O4 magnetic nanoparticles were synthesized using a co-precipitation chemical method. ► Crystal and conglomerate sizes determined by XRD and AFM, respectively, decrease with increasing Zn at% concentration. ► TEM analysis and FC and ZFC measurements are consistent with the crystal size obtained from XRD measurements. ► Co(1−x)ZnxFe2O4 magnetic nanoparticles here trend super-paramagnetic events at room hotness, as coercive fields (Hc) are small. ► Our ferrite magnetic nanoparticles can be considered as a soft magnetic material due to their low coercive magnetic field.