Impact of magnetic alignment on the structural, morphological and magnetic properties of anisotropic MnFe2O4-SiO2 composites derived from minerals

The synthesis of magnetic ceramic materials is challenging due to their tendency to crystallize in nearly isotropic structures, which hinders control over particle orientation. In this study, we investigated anisotropic MnFe 2 O 4 - SiO 2 composites produced by solid-state reaction, using natural manganese and iron ores from Rio Grande do Norte, Brazil. The samples, in powder and pellets form, were compacted at 370 MPa and sintered at 1200 ℃, for 12 hours, with the application of magnetic fields of 0.5 T, 1 T, and 2 T, along with a control sample without applied field. A phase composition of approximately 95% MnFe 2 O 4 was achieved, along with a reduction in undesirable phases and a decrease in crystallite size from 137 nm → 64 nm as the magnetic field intensity increased. Morphological analysis indicated agglomerates of triangular MnFe 2 O 4 crystals interconnected with a tridymite ( SiO 2 ) matrix. The magnetic properties showed typical soft ferrite behavior, with saturation magnetization ranging from 33 to 48 emu/g, and anisotropy observed in the direction perpendicular to the pellet plane. The magnetic anisotropy constants ranged from 3.8 × 1 0 4 to 8.7 × 1 0 4 J / c m 3 . BET analysis indicated that the porous structure was influenced by the magnetic field, with the sample exposed to 2 T exhibiting a higher specific surface area of 22.44 m 2 / g . Mössbauer and AFM analyses confirmed the influence of magnetic alignment on the microstructure and the application of magnetic fields during ceramic synthesis is effective in inducing anisotropy and enhancing the structural, morphological, and magnetic properties of functionalized composites. • Production of anisotropic Mn Fe 2 O 4 − Si O 2 composites from natural ores through solid-state reaction. • Achievement of approximately 95% Mn Fe 2 O 4 phase by reducing secondary phases under the highest vectorization magnetic field. • Reduction of crystallite size and increase in adsorbed surface area as the magnetic field intensity increased. • Agglomeration of pure triangular Mn Fe 2 O 4 crystals surrounded by a tridymite ( Si O 2 ) matrix, indicating shape anisotropy. • Magnetic alignment of particles through the preservation of magnetic domains associated with triangular morphology.