Formation of CoFe2O4/PVA-SiO2 nanocomposites: Effect of diol chain length on the structure and magnetic properties

The paper presents the influence of diol (1,2-ethanediol, 1,2-propanediol, 1,3-propanediol and 1,4-butanediol) on the formation of magnetic crystalline cobalt ferrite embedded in polyvinyl alcohol-silica hybrid matrix at 200 °C. Formation of crystalline oxides (CoFe2O4, Co3O4 and Co2SiO4) was studied by X-ray diffraction and Fourier transformed infrared spectroscopy. The effect of annealing temperature and diol chain length on the cobalt ferrite nanocrystallites size was investigated. Using transmission electron microscopy, the size and shape of particles obtained at 200 °C were recorded and compared to those obtained by annealing at 500, 800 and 1100 °C. The saturation magnetization (Ms) and coercive field were calculated from the magnetic hysteresis loops of nanocomposites. The Ms was influenced by the particle size and crystallinity only for nanocomposites annealed at 800 and 1100 °C, when the magnetic domains started to form and to be larger than the critical particle size. The diols used in the synthesis influence both the oxidic phase formation and its properties.