Effect of Mo substitution on the structural and soft magnetic properties of Li–Zn ferrites

Spinel ferrites Li0.3Zn0.4MoxFe2.3–xO4 (x = 0.00, 0.01, 0.02, and 0.03) have been prepared by the sol–gel auto-combustion method. The crystal structure, surface morphology, and magnetic properties of the samples have been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The analysis of XRD data confirms the formation of a cubic Fd-3m phase for the samples with x ≤ 0.02, while a small amount of impurity phases α-Fe2O3 and Li2MoO4 appears in the sample with x = 0.03. The lattice parameter increases at x ≤ 0.02, which indicates that the valence state of Mo ions is mainly trivalent. Both saturation magnetization (Ms) and initial permeability (μi) first decrease and then increase with increasing Mo content. The maximum initial permeability (μi) of 101 is observed at x = 0.03, which is associated with the appearance of the impurity phase α-Fe2O3 with high density. The Curie temperature increases first and then decreases with x increasing. The highest Curie temperature (Tc) of 360 °C is observed at x = 0.02, which may be suitable for higher-temperature soft magnetic materials.