Sol-Gel Fabricated CoFe2O4/SiO2 Nanocomposites: Synthesis and Magnetic Properties.

Well-defined CoFe₂ O₄ nanoparticles embedded in an amorphous SiO₂ matrix have been synthesized by a sol-gel method, characterized and investigated by Mössbauer spectroscopy and magnetic properties measurements. The mean particle size increases from 3 to 15 nm consistently with the temperature of the subsequent annealing, which varied from 800°C to 1100°C, respectively. The composites exhibit superparamagnetic behavior with the blocking temperature T_B increasing with the mean particle size from 80 to 350 K, respectively. Sufficiently high value of H_c ∼ 2.5 T (at 2 K) has been observed for the sample annealed at 1100°C. [ABSTRACT FROM AUTHOR]