Influence of Ce-Mn co-doping on the structure and magnetic properties of cobalt ferrites

In this study, we selected Ce3+ and Mn2+ as co-doped ions in order to improve the magnetic properties of cobalt ferrite. The nominal composition Co1−xMnxFe2−xCexO4 (x = 0, 0.05, 0.10, and 0.20) nanoparticles were prepared by facile co-precipitation technique, and the effect of co-doping content on the structural and magnetic properties of cobalt ferrite was investigated. The structural result confirmed the formation of cubic spinel structure for all co-doped samples, although secondary phase of CeO2 was detected in the high co-doping content ones. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bonding. All samples exhibited two frequency bands corresponding to the phonon vibrational stretching in the octahedral and tetrahedral lattice positions, respectively. The surface morphology analysis revealed the spherical shape of the ferrite nanoparticles. After co-doped with Ce3+ and Mn2+ ions, the magnetic parameters of cobalt ferrite were significantly improved. The maximum magnetization saturation is 66.5 emu/g when x = 0.05, and the maximum coercivity is 2288 Oe when x = 0.10. The two values are approximately 29% and 47% higher than that of the un-doped one. At the same time, the maximum energy product reaches 0.72 MG·Oe, which is about 118% higher than that for pure cobalt ferrite, i.e. 0.33 MG·Oe. The reasons may be related to the substitution of Fe3+ and Co2+ with Ce3+ and Mn2+, and also the resulting changes in crystallite sizes of the samples. These results demonstrate the effectivity of Ce-Mn co-doping in improving the magnetism of cobalt ferrite.