Structure and magnetic properties of cobalt ferrite foam with low mass density

It is extremely desirable but challenging to develop a facile synthesis to directly prepare permanent magnet foam with high coercivity (Hc) and low mass density to meet the requirements of advanced magnets in modern industry. In this work, we developed a facile strategy to synthesize cobalt ferrite foam by solution combustion method and subsequently annealing treatment. The structure and magnetic properties of the foams can be influenced by the ratios of glycine to nitrate (G/N), Co content and annealing treatment temperatures. The increase in the mean grain sizes within the single domain range gives rise to an enhancement in coercivities. The highest Hc of ∼3 kOe with an ultra-low mass density of ∼45 mg/cm3 can be successfully obtained by controlling the preparation process. The work opens up a new way to prepare ultra-light Fe-based oxides for magnetic and catalytic applications. •Foam-like porous CoxFe3-xO4 was prepared by facile auto-combustion method.•The effects of glycine to nitrate ratios and Co content were studied.•Ultra low mass density ∼45 mg/cm3 and large coercivity ∼3 kOe were obtained.