VARIATION IN MAGNETIC PROPERTIES OF SOL-GEL-SYNTHESIZED COBALT FERRITES

Single-phase cobalt ferrite (CoFe2O4) was synthesized with a sol-gel reaction between 10.59 g of cobalt nitrate and 29.40 g of iron nitrate using 480 mL of 10 % polyvinyl alcohol (PVA) in water. Their magnetic squareness and coercive field were slightly reduced with the increase in the annealing at 800 degrees C from 2 h to 6 h. To examine the reproducibility of ferrite products of the PVA sol-gel method, the synthetic condition was repeated 28 times. After annealing for 4 h, CoFe2O4 samples from different batches exhibit variations in the magnetic properties. The coercive field has a large distribution because of its sensitivity to the particle agglomeration, whereas the squareness fluctuates in a narrower range from 0.22 to 0.29. Since the squareness is the ratio of the remanence to the saturation magnetization, the particle agglomeration tends to increase both values while keeping this ratio rather unchanged.