Structural and Magnetic Properties of Mn $^{3+}$ Substituted Ordered and Disordered Li $_{0.5}$ Cr

A series of Li_0.5Mn_xCr_0.5Fe_2-xO₄ (x = 0.0-1 in the steps of 0.25) were synthesized by sol-gel auto combustion method, aiming to study the structural, magnetic and dielectric properties of ordered and disordered Li-ferrite related to the concentration of the substituted Mn³⁺ ions. X-ray diffraction measurements were used for analyzing the structural parameters of the prepared samples. Superstructure lines are observed for Li_0.5Cr_0.5Fe₂O₄ and disappear at higher levels of Mn³⁺ substitution. TEM images demonstrate that the particle size is uniform and are in good crystalline form. Saturation magnetization decreased from 51 to 24 emu/g, whereas coercivity varies from 90-170 Oe with Mn³⁺ substitution. Permeability measurements were carried out as a function of temperature. Initial permeability (μ_i)decreased with the increasing Mn³⁺ substitution. The dc resistivity increased with the Mn³⁺ substitution. Dielectric constant decreased with the increasing frequency and it also decreased with the increasing Mn³⁺ substitution.