Systematic Study on the Synthesis and Magnetism Properties of Manganese Ferrite MnFe2O4 by an Oxidation Roasting Process

A low-cost and high-efficiency solid reaction method has been reported as an effective technology to synthesize manganese ferrite MnFe2O4 with a spinel crystal structure. This work clarified the underlying reason for the influence mechanism of SiO2 and Al2O3 on the synthesis of MnFe2O4. Synthetic MnFe2O4 polyhedral microparticles with a saturated magnetization of 71.19 emu/g, a ratio of saturation magnetization to residual magnetization (Ms/Mr) of 0.062 and a coercivity (Hc) of 6.50 Oe were successfully obtained at an oxidization roasting temperature of 1100 °C for 60 min. The experimental results indicate that the tetrahedral Mn2+ ions and octahedral Mn3+ ions in the crystal structure of manganese ferrite MnFe2O4 were replaced by tetrahedral Si2+ ions and octahedral Al3+ ions from (Mn2+)x(Fe2+)y(Si2+)1−x−y[Fe3+]2O4 and (Mn2+)[Fe3+]2−x[Al3+]xO4, respectively. In addition, hercynite FexMn1−xAl2O4 with a spinel crystal structure and olivine MnxFe2−xSiO4 with an orthorhombic crystal structure were partially formed in the synthesis of manganese ferrite MnFe2O4, in which some Fe2+ ions were easily replaced by Mn2+ ions to form stable hercynite MnAl2O4 and olivine Mn2SiO4 in these crystal structures. The current research work provides comprehensive insights for synthesizing manganese ferrite MnFe2O4 and continuously advances its technical progress.