Hydrothermal synthesis of Co_yZn_yMn_1-2yFe₂O₄ nanoferrites: Magneto-optical investigation

Manganese ferrites nanoparticles (NPs) substituted with both Co²⁺ and Zn²⁺ simultaneously (Co_yZn_yMn_1-2yFe₂O₄ NPs for y=0.0 to 0.5), have been produced by hydrothermal approach. The substitution with both Co²⁺ and Zn²⁺ ions on the structure, spectroscopic and magneto-optical properties of nanocrystalline MnFe₂O₄ spinel ferrites have been analyzed in detail. The formation of spinel phase and structural changes induced by Co²⁺ and Zn²⁺ ions substitutions were confirmed by X-ray diffraction studies. Rietveld refinement revealed the cubic spinel phase for all products (minor amount of Fe₂O₃). Lattice constant and crystallite size were found to decrease from 8.478 to 8.370 Å and from 14.68 to 8.22 nm, respectively with increasing substitution of Co²⁺ and Zn²⁺ ions. HR-SEM and HR-TEM micrographs revealed the high homogeneity cubic structure of samples. The hyperfine magnetic field values for all products after Mn²⁺, Zn²⁺ and Co²⁺ ions substitution were determined by Mössbauer analysis. The estimated optical E_g (Energy band gap) values are in the range of 1.41–1.54 eV for the samples. The smaller E_g values are mainly attributed to greater particle size and decreasing quantum confinement effect.