Tuning the magnetic properties of ferrite nanoparticles by Zn and Co doping

Abstract This work describes the synthesis of ferrite nanoparticles and the zinc and cobalt doping effect on tuning their magnetic properties. The zinc doping led to formation of a secondary crystalline phase (ZnO), which meant that the Zn and Co individual ions show different physical-chemical affinities for the two types of lattice sites. Zero-field cooling and field cooling curves were elaborated to study the magnetization unblocking process of these nanoparticles. The metal doping effect led to large differences in the magnetization curves. The zinc-doped samples were shown to exhibit classical magnetization unblocking, being superparamagnetic below the room temperature. The cobalt doping increased the blocking temperature to above room temperature. The amount of cobalt did not change the coercive field of the doped samples. The coercive field of zinc-doped samples followed the same trend, but with a much lower value (0.6 kOe) when compared with cobalt-doped samples (18 kOe), showing a great change in magnetic anisotropy. The current synthesis approach offered a facile way to synthesize ferrite nanoparticles with metal doping-tunable magnetic properties by an environmentally friendly and facile sol-gel approach using water as solvent. This finding motivated us to think these ferrite nanoparticles can be attractive for biomedical and/or technological applications, although further studies other than these are still required.