Synthesis and characterization of low temperature superparamagnetic cobalt ferrite nanoparticles Synthesis and characterization of low temperature superparamagnetic cobalt ferrite nanoparticles
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 © IAAM-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.