Investigation of the structure and magnetic properties of Sn substituted Li-Zn ferrites fabricated by sol–gel process

A series of Sn doped Li-Zn ferrite powders with composition of Li(0.2+0.5x)Zn0.6SnxFe(2.2−1.5x)O4 (x = 0.00, 0.02, 0.04, 0.06, and 0.08) are synthesized by sol–gel process. The ring-shaped bulk samples of all compositions are obtained by sintering at 950 °C for 3 h, and all the structural and magnetic measurements were carried out on the sintered bulk samples. X-ray diffraction (XRD) patterns confirmed the formation of single-phase spinel structure when x ≤ 0.06 and the second phase of SnO2 at x = 0.08. Field emission scanning electron micrograph (FE-SEM) is used to observe the surface morphology of the bulk samples and particle sizes (DSEM). Micrograph of the sample for x = 0.08 shows many small particles appearing on the surface of the aggregation bulk samples. Vibrating sample magnetometer (VSM) is employed to study the saturation magnetization (Ms) and coercivity (Hc). The Ms displays a downtrend with the increasing of doping concentration and all samples have a lower coercivity of less than 30 Oe. Initial permeability (μi) and Curie temperature (Tc) are measured in a furnace using HP4294A impedance analyzer. The μi increases with the Sn4+ concentration until x = 0.06 and the Tc decreases with the Sn4+ concentration. The cation distribution estimated from XRD pattern and magnetic properties analyses suggest that Li+ ions appear in the tetrahedral sites with increasing of Sn4+ and Li+ contents.