2011 年 119 巻 1390 号 p. 541-543
Controlling magnetic properties of sol–gel synthesized cobalt ferrites (CoFe2O4) have been studied by variations in amount of polyvinyl alcohol (PVA) and annealing temperature. PVA of 24, 32, 40 and 48 g in 10% w/v aqueous solutions was used in the reaction between 10.592 g of Co(NO3)2·6H2O and 29.407 g of Fe(NO3)3·9H2O. The decrease in PVA led to the reductions in coercive field and squareness. However, X-ray diffraction peaks indicated that iron oxide (α-Fe2O3) and iron oxide hydroxide [FeO(OH)] were also formed when the PVA was less than 48 g. The optimized amount for obtaining single phase CoFe2O4 was therefore 48 g which was used for studies of heat treatment effect. Both coercive field and squareness were increased with the increase in annealing temperature from 280 to 680°C and then reduced with the further increasing temperature up to 900°C as a result of particles agglomeration.
