Structural and magnetic characterizations of Cd substituted nickel ferrite nanoparticles

Nanocrystalline samples with stoichiometric composition and general formula of Ni1-xCdxFe2O4 (x=0.0, 0.1, 0.3, 0.5, and 0.7) were synthesized by the sol-gel auto-combustion method. Structure and crystallite size were analyzed using X-ray diffraction data and revealed spinel mono-phase formation in the range of nanometric crystallite size (12-31 nm), which was also confirmed using field emission scanning electron microscopy (FE-SEM). The absence of the organic phase and spinel formation were monitored by Fourier transform infrared (FTIR) spectroscopy. Saturation magnetization at room temperature was found to increase with Cd content up to x=0.3 and then tended to decrease for x>0.3. Increase in magnetic moment with Cd is explained by Neel's two-sublattice (tetra and octahedral sublattice) collinear models, according to which the magnetic moment is the vector sum of the lattice magnetic moment. Decrease in magnetization for x>0.3 samples could be explained by Yafet-Kittel model. Also, coercivity was decreased by increasing Cd content due to the decrease of magnetocrystalline anisotropy constant of the samples.