Synthesis and magnetic properties of nanocrystalline CoFe ₂O ₄ ferrite by using spraying-coprecipitation method

Nanocrystalline CoFe ₂O ₄ ferrite was successfully prepared by the spraying-coprecipitation method. The effect of temperature on microstructure and magnetic properties was investigated. The results show that uniform and fine nanocrystalline CoFe ₂O ₄ ferrite powders are obtained by the spraying-coprecipitation method. The grain size is about 29 nm calcined at 600°C for 1.5h. There are a few agglomerates with average sizes below 100nm. The specific saturation magnetization of nanocrystalline CoFe ₂O ₄ ferrite increase with the calcining temperature of specimens at room temperature, and Ms is 88.6 A · m ² · kg ^-1 as the calcining temperature is 850°C. When the grain size is 29nm, the maximal coercivity Hc of nanocrystalline CoFe ₂O ₄ ferrite arrives at 64.5kA · m ^-1, then it decreases with the increase of the grain size. The results may be attributed to the effect of grain size in nanocrystalline magnetic materials.