Sol–gel auto combustion synthesis of CoFe2O4/1-methyl-2-pyrrolidone nanocomposite with ethylene glycol: Its magnetic characterization

Magnetic nanoparticles were generated by sol–gel auto combustion synthesis of metal salts in the presence of 1-methyl-2-pyrrolidone, a functional solvent and ethylene glycol as usual solvent. The average crystallite size was obtained by using line profile fitting as 11 ± 5 nm. The saturation magnetization value decreases with usage of the ethylene glycol in synthesis. The observed exchange bias effect further confirms the existence of the magnetically ordered core surrounded by spin-disordered surface layer and the ethylene glycol. Square-root temperature dependence of coercivity can be fitted to Knellerʹs law in the temperature range of 10–400 K. The reduced remanent magnetization values lower than the theoretical value of 0.5 for non-interacting single domain particles indicate the CoFe2O4-1-methyl-2-pyrrolidone nanocomposite to have uniaxial anisotropy instead of the expected cubic anisotropy according to the Stoner–Wohlfarth model.