Synthesis and characterization of Ni1−xCoxFe2O4 nanoparticles

Ni_1−xCo_xFe₂O₄ (x=0.6, 0.8 and 0.9) nanoparticles have been synthesized with various crystallite sizes depending on the thermal treatments and composition (cobalt content) using the sol-gel combustion method. The size of nanoparticles has been controlled by thermal treatment. On the other hand, the magnetic property of the ferrite has been controlled by changing the heat treatment. Morphology and particle sizes of Ni_1−xCo_xFe₂O₄ have been studied using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The presence of functional group has been identified by Fourier Transform Infrared (FTIR) spectra. From TGA-DTA studies, the weight gains of Ni_1−xCo_xFe₂O₄ nanoparticles have been observed and it might be due to capping organic molecules with oxygen at temperatures above 200 °C. Magnetic properties of Ni_1−xCo_xFe₂O₄ particles have been analysed using VSM and it is found that saturation magnetization (M_s) has increased with particle size and has coercivity (H_c) increased initially and then decreased. The M_s and H_c values decreased with the increase of content of cobalt in Ni_1−xCo_xFe₂O₄.