Mechanisms Influencing Ferromagnetic Resonance Linewidth in Ca–In–Sn Co-Substituted Yttrium–Iron Garnet Ferrites

With the rapid development of communication technologies such as 5G, yttrium iron garnet (YIG) has been widely applied in microwave devices and other systems owing to its low ferromagnetic resonance linewidth. Loss reduction and effects of doping on performance have been important research areas for garnet ferrite. This study prepared Ca²⁺, In³⁺, and Sn⁴⁺ codoped YIG ferrite samples with the chemical formula Y_3-<i>x</i>Ca<i>_x</i>Fe_{5-<i>x</i>-<i>y</i>}In<i>_y</i>Sn<i>_x</i>O₁₂ (<i>x</i> = 0.05-0.3) (<i>y</i> = 0.2, 0.45) via solid-state reaction. The analyses of the crystal structure, micromorphology, and magnetic properties enabled the identification of the causes of variations in parameters, such as saturation magnetization and coercivity. Theoretical calculations of the anisotropy constants clarified the patterns upon substituting Fe³⁺ with In³⁺ and Sn⁴⁺, revealing a shift in the positions of Fe³⁺ substitution. Finally, the primary factors influencing loss were identified, and the key process parameters influencing performance were determined. The resulting polycrystalline garnet ferrite exhibited an extremely low ferromagnetic resonance linewidth parameter (ΔH = 29 Oe) and a high density (>5.2 g/cm³). This study provides specific guidance on process parameters and element selection for high-performance, low-loss YIG materials, as well as a detailed theoretical explanation of the performance changes resulting from co-doping YIG with In³⁺ and Sn⁴⁺.