Structural, physical, and magnetic properties of nanocrystalline manganese-substituted lithium ferrite synthesized by sol–gel autocombustion technique

Nanoparticles of spinel ferrite Li 0.5–0.5 x Mn x Fe 2.5–0.5 x O 4 ( x = 0, 0.25, 0.5, 0.75 and 1) were prepared by sol–gel autocombustion technique. The crystalline phase formation, morphology, cation distribution, and magnetic properties of Li 0.5–0.5 x Mn x Fe 2.5–0.5 x O 4 nanoferrite samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectroscopy, and vibrating sample magnetometer (VSM). The lattice parameter increases by Mn substitution, while both the crystallite size and Curie temperature ( T C ) decrease. Values for both the saturation magnetization ( M s ) and the coercivity ( H c ) were enhanced because both are larger for Mn-substituted samples than those for unsubstituted ones. The addition of Mn 2+ ions promotes ( M s ) until ( x = 0.5) then an appreciable decrease occurs, whereas the coercivity ( H c ) increases up to x = 0.25 then it decreases. The role of the substitution with Mn 2+ ions in changing all investigated properties of lithium ferrite was explained according to different theories.