Document Type : Research Paper
School of Metallurgy & Materials Engineering, Iran University of Science and Technology (IUST), Tehran, Iran
Cobalt ferrite (CoFe2 O4 ) nanoparticles have attracted significantly attentions for spintronics, recording media and bioapplications due to their unique magnetic and chemical properties. In this work, single phase CoFe2 O4 nanoparticles were synthesized at various coprecipitation temperatures (60, 80 and 90 °C) without post calcination. The effects of oleic acid as surfactant on the microstructure, magnetic properties and heating rate were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and vibrating sample magnetometry techniques. The small particle size and narrow size distribution were achieved using oleic acid. IR spectra showed the oleic acid molecules adsorbed on particle surface, leading to the lower growth rate and then the smaller nanoparticles. The CoFe2 O4 nanoparticles showed ferromagnetic behavior. The highest saturation magnetization of 45 emu/g and coercivity of 950 Oe were achieved at the coprecipitation temperature of 80 °C without using oleic acid. However, the saturation magnetization increased from 8 to 37 emu/g with the coprecipitation temperature due to the increase of crystallinity and particle size. The coprecipitated CoFe2 O4 nanoparticles at 80 °C exhibited the AC heating temperature of 7.5°C and specific loss power of 18.3 W/g under magnetic field of 100 Oe and frequency of 200 kHz. The heat generation mechanism was attributed to the hysteresis loss.