Synthesis and Magnetic Properties of Zn, Co and Ni Substituted Manganese Ferrite Powders by Sol-gel Method

The Zn, Co and Ni substituted manganese ferrite powders, Mn1-x(Zn, Co, Ni)(x)Fe2O4, were fabricated by the sol-gel method, and their crystallographic and magnetic properties were studied. The Zn substituted manganese ferrite, Zn0.2Mn0.8Fe2O4, had a single spinel structure above 400 degrees C, and the size of the particles of the ferrite powder increased when the annealing temperature was increased. Above 500 degrees C, all the Mn1-x(Zn, Co, Ni)(x)Fe2O4 ferrite had a single spinet structure and the lattice constants decreased with an increasing substitution of Zn, Co, and Ni in Mn1-x(Zn, Co, Ni)(x)Fe2O4. The Mossbauer spectra of Mn1-xZnxFe2O4 (0.0 <= x <= 0.4) could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe3+ ions. For x = 0.6 and 0.8 they showed two Zeeman sextets and a single quadrupole doublet, which indicated they were ferrimagnetic and paramagnetic. And for x = 1.0 spectrum showed a doublet due to a paramagnetic phase. For the Co and Ni substituted manganese ferrite powders, all the Mossbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe3+ ions. The variation of the Mossbauer parameters are also discussed with substituted Zn, Co and Ni ions. The increment of the saturation magnetization up to x = 0.6 in Mn1-xCoxFe2O4 could be qualitatively explained using the site distribution and the spin magnetic moment of substituted ions. The saturation magnetization and coercivity of the Mn1-x(Zn, Co, Ni)(x)Fe2O4 (x = 0.4) ferrite powders were also compared with pure MnFe2O4.