The role of pH on the particle size and magnetic consequence of cobalt ferrite

• CoFe2O4 nanoparticles were prepared by co-precipitation method at different pH.
• Τhe single cubic phase with the average crystallite sizes of 5–24 nm were formed.
• Cation distribution in tetrahedral and octahedral sites was estimated using XRD data.
• The sample synthesized at pH~8 and 9 showed superparamagnetic behavior.
• The crystallinity and crystallite size were increased by increasing the pH.

Cobalt ferrite (CoFe2O4) nanoparticles with various size distributions were prepared by a chemical co-precipitation method at different pH condition from 8 to 13. The structural characterizations of the prepared samples were carried out using powder X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscope. The XRD results revealed that a single cubic CoFe2O4 phase with the average crystallite sizes of about 5–24 nm were formed. Cation distribution occupancy in tetrahedral and octahedral sites were estimated by employing Rietveld refinement technique. The results showed that the whole series of samples contain a partial inverse spinel structure. FTIR measurements between 370 and 4000 cm−1 confirmed the intrinsic cation vibrations of spinel structure of the samples. The room temperature magnetic properties of the samples have been examined using vibrating sample magnetometer. It is found that with increasing the pH of reaction, the magnetization and coercive field could be increased. The sample synthesized at pH~8 and 9 showed superparamagnetic behavior and highest coercive field up to 650 Oe is attributed to the sample synthesized with pH~13.