CoFe₂O₄ nanocrystalline powders prepared by citrate-gel methods: Synthesis, structure and magnetic properties

Nanocrystalline CoFe₂O₄ powders were prepared by decomposition of metal ion citrate precursors. Four samples were synthesized from precursor solutions having different pH values in the range <1-7.0. The powders were characterized by X-ray Diffraction, Thermogravimetry, Differential Thermal Analysis, N₂ physisorption and Transmission Electron Microscopy. Magnetic properties were explored by a SQUID magnetometer. Three out of the four samples, coming from solutions of pH 2, 4 and 7, were produced by an autocombustion reaction and are very similar as regards average size of the nanoparticles (about 20 nm), their morphology and the magnetic properties, while the fourth sample was produced by a slower thermal decomposition and is composed of smaller nanoparticles (about 10 nm).