Effect of Valence Floating on the Magnetic Properties of Ca–Sn Co-Doping Y_3−xCa_xFe_5−xSn_xO₁₂(x = 0–0.25)

First-principle calculations were used to simulate the changes in magnetic parameters and interatomic charge density in the crystal structure of yttrium iron garnet (YIG) caused by Ca–Sn co-doping. The simulation results illustrate that Ca and Sn have no spin polarization in the crystal, and the charge density among ions tends to increase with doping concentration. A solid-state reaction method was employed to prepare YIG with varying concentrations of Ca–Sn co-doping. The saturation magnetization ( $4\pi M_{s}$ ) of the material shows an initial increase and then decrease as the number of doping increases. This phenomenon of increment in $4\pi M_{s}$ at first could be accounted for the increase of the net magnetic moment of material. The reduction in $4\pi M_{s}$ could be interpreted as the content of Fe ³⁺ ( $5~\mu \text{B}$ ) decreases, while the Fe ²⁺ ( $4~\mu \text{B}$ ) in the material becomes the primary portion when the concentration of doping exceeds 0.10.