Tuning the optical band gap and magnetization of oleic acid coated CoFe2O4 NPs synthesized by facile hydrothermal route

The high-quality oleic acid coated cobalt ferrite (OCF) nanopowders were prepared by hydrothermal route at 60 degrees C, 120 degrees C and 180 degrees C temperatures. The average crystallite sizes of 5.2 +/- 0.07 nm, 13.3 +/- 0.19 nm and 18.9 +/- 0.23 nm were evaluated for OCF-60, OCF-120 and OCF-180. The SEM images of OCF exhibits agglomerated nanoparticles of roughly spherical shape. Optical energy gap was estimated and found to be enhanced from 1.8 to 2.3 eV with decreasing particle size. The area ratio A(nu 2) of phonon modes occurred at 447 and 600-613 cm(-1) are correspond to octahedral and tetrahedral sites, respectively. The enhancement in saturation magnetization MS was observed from 44.64 to 76.66 (emu/g) owing to decrease in area ratio A(nu 2). Value of spin-spin correlation function was found to be decreased from 1.60 to 0.93 with increase in M-S/size. A strong correlation between magnetic and optical properties with particle size was observed.