Some Electrical and Magnetic Properties of Garnets

Polycrystalline specimens have been prepared of yttrium‐iron garnet (YIG) and substituted garnets of the forms $3{\mathrm{Y}}_2{\mathrm{O}}_3\text{·(5−x)}{\mathrm{Fe}}_2{\mathrm{O}}_3\mathrm{·x}{\mathrm{Ga}}_2{\mathrm{O}}_3$ and $\text{(3−x)}{\mathrm{Y}}_2{\mathrm{O}}_3\mathrm{·x}{\mathrm{R}}_2{\mathrm{O}}_3\text{·5}{\mathrm{Fe}}_2{\mathrm{O}}_3$ , where $\mathrm{R}$ represents a rare earth element. Measurements have been made of lattice constants, magnetic moments, dc conductivity, permittivity, and permeability. The permeability and magnetic losses were measured from dc to 2 kMc. Density has a large effect on the low‐frequency initial permeability; values varied from 14 to 170 for the YIG samples studied. Nominal room temperature properties of YIG are: $\text{a\hspace{0.17em}=\hspace{0.17em}12.374±0.005\hspace{0.17em}}\mathrm{A}$ ; ${\mu }_i{\mathrm{\prime /\mu }}_0\text{∼70\hspace{0.17em}}\mathrm{at}\text{\hspace{0.17em}1\hspace{0.17em}}\mathrm{Mc}\text{,\hspace{0.17em}∼10\hspace{0.17em}}\mathrm{at}\text{\hspace{0.17em} 100\hspace{0.17em}}\mathrm{Mc}\text{,\hspace{0.17em}∼1\hspace{0.17em}}\mathrm{at}\text{\hspace{0.17em}1\hspace{0.17em}}\mathrm{kMc}$ ; ${\text{ρ\hspace{0.17em}=\hspace{0.17em}10}}^{10}\hspace{0.17em}\mathrm{ohm}‐\mathrm{cm}$ ; ${\mathrm{\epsilon \prime /\epsilon }}_0\text{∼12\hspace{0.17em}}\mathrm{at}\text{\hspace{0.17em}20\hspace{0.17em}}\mathrm{Mc}$ ; $\text{μβ\hspace{0.17em}=\hspace{0.17em}6.8\hspace{0.17em}}\mathrm{Bohr}\hspace{0.17em}\mathrm{magnetons}\hspace{0.17em}\mathrm{per}\hspace{0.17em}\mathrm{formula}\hspace{0.17em}\mathrm{weight}$ . Gallium substitution increased the conductivity but decreased the other quantities measured. Rare earth substitutions had significant effects on the magnetic moments but produced only slight changes in the other quantities. The permeability spectrum of dysprosium‐substituted YIG clearly shows a domain wall absorption peak at 400 kc and a spin‐resonance absorption at 400 Mc.