Synthesis and characterization of low temperature superparamagnetic cobalt ferrite nanoparticles
Kamlesh V. Chandekar*, K. Mohan Kant
Department of Applied Physics, Visvesvararya National Institute of Technology, Nagpur 440010, India
Adv. Mater. Lett., 2017, 8 (4), pp 435-443
Publication Date (Web): Mar 14, 2017
Copyright © 2019 VBRI Press
Cobalt ferrite (CoFe2O4) nanoparticles were synthesized by co-precipitation route at 80 °C. X-ray diffraction pattern (XRD) confirmed cubic inverse spinel structure of CoFe2O4 nanoparticles. The average crystallite size of CoFe2O4 nanoparticles estimated by X-ray line profile fitting was 12±2 nm for high-intensity peak (311). The particle size, distribution and surface morphology was estimated using Transmission electron microscopy (TEM) with average particle size of 16±2 nm. Raman spectra of CoFe2O4 nanoparticles exhibits phonon modes corresponding to tetrahedral sites (679 cm-1) and octahedral sites (465 cm-1) respectively. The saturation magnetization Ms for CoFe2O4 sample is found to be 63 and 82 emu/g at 300 K and 10 K respectively. The cubic magnetic anisotropy constant K1 and saturation magnetization Ms are obtained by fitting M versus H isotherm to the saturation approach law. By fitting, K1 and Ms is 2.16 x105 J/m3 and 66 emu/g respectively at 300 K. The cubic magnetic anisotropy constant K1 = 5.49 x105 J/m3 is evaluated at blocking temperature of 144 K. The particle size and L-S coupling is responsible for superparamagnetic behaviour of CoFe2O4 nanoparticles. Fitting of FC curve provides Curie temperature at Tc = 823K using modified Bloch’s law for CoFe2O4 nanoparticles. Tunable particle sizes by controlling the magnetic anisotropy and L-S coupling will tailor magnetic properties and usage in bio-medical applications
CoFe2O4,co-precipitation, L - S coupling, superparamagnetism, anisotropic constant.