Anisotropy and magnetostriction of germanium-substituted yttrium iron garnet

The anisotropy, magnetostriction, and linewidth of germanium‐substituted yttrium iron garnet single crystals of the composition $\{{\mathrm{Y}}_{\text{3−x}}{\mathrm{Me}}_x^{\mathrm{II}}\mathrm{\}\hspace{0.17em}[}{\mathrm{Fe}}_2\mathrm{](}{\mathrm{Fe}}_{\text{3−y−z}}{\mathrm{Me}}_y^{\mathrm{IV}}{\mathrm{Fe}}_z^{\mathrm{II}}){\mathrm{O}}_{\text{12−δ}}{\mathrm{F}}_{\delta }{\mathrm{(Me}}^{\mathrm{II}}={\mathrm{Ca}}^{\text{2+}},{\mathrm{Pb}}^{\text{2+}},\mathrm{and}{\mathrm{Me}}^{\mathrm{IV}}={\mathrm{Ge}}^{\text{4+}},{\mathrm{Si}}^{\text{4+}})$ have been studied by means of ferromagnetic resonance. Analysis data of Fe²⁺, Ge⁴⁺, and of the impurities Pb²⁺, Ca²⁺, Si⁴⁺ and F⁻ are given for all crystals as well as optical‐absorption coefficients in the wavelength range 1–2.5 μm. The resonance measurements have been carried out at 9.25 GHz in the temperature range 4.2–460 °K. A comparison of the temperature dependence of the anisotropy contributions caused by Fe²⁺ with the single‐ion model leads to a good agreement. However, it has to be assumend that only one‐third of the Fe²⁺ ions are effective. The contribution to the magnetostriction constants turns out to be positive for both λ₁₀₀ and λ₁₁₁. Maxima of the resonance linewidth were observed at about 40 and 370 °K.