Temperature dependent magnetic properties of CoFe2O4/CTAB nanocomposite synthesized by sol gel auto-combustion technique

A CoFe2O4/cetyl trimethylammonium bromide (CTAB) nanocomposite has been fabricated by a sol gel auto-combustion method. Characterization of the material revealed the composition of the crystalline phase as CoFe2O4 while FT-IR confirmed the presence of CTAB on the nanoparticles. From X-ray line profile fitting, average crystallite size was estimated to be 22 +/- 6 nm. SEM analysis showed a porous sheet-like morphology with internal nanosize grains of about 30 nm. The room temperature coercive field (He) of the CoFe2O4/CTAB nanocomposite was found to be 1045 Oe which is close to the previously reported room temperature values for bulk CoFe2O4. The H-c, was observed to decrease almost linearly with the square root of the temperature (root T) according to Kneller's law. From the linear fit of H-c versus root T, the zero-temperature coercivity (H-c0) and superparamagnetic blocking temperature (T-B) of the CoFe2O4/CTAB nanocomposite were found to be similar to 9.1 kOe and similar to 425 K, respectively. The remanence magnetization (M-r), the reduced remanent magnetization (M-r/M-s), and the effective magnetic anisotropy (K-eff) decrease with increasing temperature. The M-r/M-s value of 0.6 at 10 K higher than the theoretical value of 0.5 for non-interacting single domain particles with the easy axis randomly oriented suggests the CoFe2O4/CTAB nanocomposite to have cubic magnetocrystalline anisotropy according to the Stoner Wohlfarth model. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.