Magnetic Properties of CoFe_2O_4 Spinels Prepared from Layered Cobalt-iron(II)-iron(III) Hydrotalcite Precursors

Co-Fe(Ⅱ) -Fe(Ⅲ) hydrotalcite precursors with different Co2+/Fe2+/Fe3+ molar ratios were prepared by chemical coprecipitation. Then nanosized Co-ferrite particles were obtained by calcining the precursors at 900℃ . The specimens were charactered by XRD,IR and VSM. When the Co2+/Fe2+/Fe3+ molar ratio in the stock solution is equal to(a) 1/3/1,(b) 3/5/2,(c) 1.92/1/2,(d) 2/1/1 and(e) 3/1/1,we can get layered precursors,and the spinel ferrites were obtained by calcining Co-iron(Ⅱ) -iron(Ⅲ) hydrotalcite precursors at high temperature. Phase components of the product got from different molar ratio of precursors are not the same. When M2+/M3+molar ratio is close to 1/2,the stoichiometric ratio,the single phase CoFe2O4 ferrite can be obtained. At the same,maximum coercivity of 116kA/m,and also the saturation and residual magnetization of 72.63 A·m2/kg and 23.37 A·m2/kg were obtained.