Enhanced magnetostrictive properties of CoFe2O4 synthesized by an autocombustion method

The magnetostrictive properties of sintered cobalt ferrite derived from nanocrystalline powders synthesized by three different low-temperature methods (citrate, coprecipitation and autocombustion) and the high-temperature ceramic method have been compared. A strong dependence of the magnetostrictive strain is observed on the initial morphology of the ferrite particles and the microstructure of the final sintered product. The nanoparticles synthesized by the autocombustion method, with a flaky and porous morphology, give a sintered material with small grains. Maximum magnetostriction is found to be decreased with increasing grain size. However, no correlation is observed between the initial particle size of the powders or the sintered density and magnetostriction. Maximum magnetostriction values of 197, 184, 159, and 135 ppm are obtained for the sintered samples with average grain sizes of 8 mu m (combustion), 17 mu m (citrate), 23 mu m (coprecipitation), and > 25 mu m (ceramic), respectively. (c) 2007 Elsevier B.V. All rights reserved.