Abstract
A magnetic nanocomposite was generated by the sol-gel auto-combustion method in the presence of 1-methyl-2-pyrrolidone, a functional solvent. The temperature-dependent magnetic properties of the CoFe2O4 nanoparticles have been extensively studied in the temperature range of 10-400 K and magnetic fields up to 80 kOe. Zero field cooled (ZFC) and field cooled (FC) curves indicate that the blocking temperature (T-B) of the CoFe2O4 nanoparticles is above 400 K. It was found from M-H curves that the low temperature saturation magnetization values are higher than bulk value of CoFe2O4. The saturation magnetization (M-s), remanence magnetization (M-r), reduced remanent magnetization (M-r/M-s) and coercive field (H-c) values decrease with increasing temperature. The M-r/M-s value of 0.75 at 10 K indicates that the CoFe2O4 nanoparticles used in this work have, as expected, cubic magnetocrystalline anisotropy according to the Stoner-Wohlfarth model. T-1/2 dependence of the coercive field was observed in the temperature range of 10-400 K according to Kneller's law. The extrapolated T-B and the zero-temperature coercive field values calculated according to Kneller's law are almost 427 K and 13.2 kOe, respectively. The room temperature H-c value is higher than that of the previously reported room temperature bulk values. The effective magnetic anisotropy constant (K-eff) was calculated as about 0.23 x 10(6) erg/cm(3) which is lower than that of the bulk value obtained due to disordered surface spins. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.