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 (Hc) 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 Hc was observed to decrease almost linearly with the square root of the temperature (√T) according to Kneller's law. From the linear fit of Hc versus √T, the zero-temperature coercivity (Hc0) and superparamagnetic blocking temperature (TB) of the CoFe2O4/CTAB nanocomposite were found to be ∼9.1 kOe and ∼425 K, respectively. The remanence magnetization (Mr), the reduced remanent magnetization (Mr/Ms), and the effective magnetic anisotropy (Keff) decrease with increasing temperature. The Mr/Ms 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.