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Nickel Substitution Effects on Nano-sized Co, Mn and MnZn Ferrites Synthesized by Sol-gel Method
Nickel substituted nano-sized ferrite powders, Co1-xNixFe2O4, Mn1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 (0.0 ≤ x ≤0.2), were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently compared. The lattice constants decreased as quantity of nickel substitution increased, while the particle size decreased in Co1-xNixFe2O4 ferrite but increased for the Mn1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 ferrites. For the Co1-xNixFe2O4 and Mn1-xNixFe2O4 (0.0 ≤ x ≤ 0.2) ferrite powders, the Mössbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe3+ ions. However, the Mössbauer spectrum of Mn0.8 Zn0.1Ni0.1Fe2O4 consisted of two Zeeman sextets and one single quadrupole doublet due to the ferrimagnetic and paramagnetic behavior. The area ratio of the Mössbauer spectra could be used to determine the cation distribution equation, and we also explain the variation in the Mössbauer parameters by using this cation distribution equation, the superexchange interaction and the particle size. The saturation magnetization decreased in the Co1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 ferrites but
increased in the Mn1-xNixFe2O4 ferrite with nickel substitution. The coercivity decreased in the Co1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 ferrites but increased in the Mn1-xNixFe2O4 ferrite with nickel substitution. These variations could thus be explained by using the site distribution equations, particle sizes and spin magnetic moments of the substituted ions.