Physical and microwave characteristics of Gd-doping yttrium iron garnet (YIG)*

Ferrimagnetic insulating yttrium iron garnet (YIG) are widely used in microwave devices due to their unique magnetic, electrical and microwave properties. The substitution of rare earth ion for the Y$^{3+}$ ion can modulate or improve its high-frequency properties for microwave application. We prepared a serial of single-phased polycrystalline Y$_{3-x}$Gd$_{x}$Fe$_{5}$O$_{12}$ garnet samples with $x $= -- 3.0 by the conventional ceramic technique. The refinement of X-ray diffraction patterns of the samples shows them to crystallize in a centrosymmetrically cubic structure with a\textit{ Ia3d} space group. Both the lattice constant and dc saturation magnetization at room temperature decrease with increasing Gd$^{3+}$ We also measured the low- and high-frequency dielectric constant and tangent loss. As well, the spin wave line width $\Delta $H$_{k}$ regarding the ferromagnetic resonance behavior is on progress. These results are important to develop high-power circulators and isolators in microwave range.