Magnetostriction of Ruthenium-Substituted Yttrium Iron Garnet

The contribution to the magnetostriction constants ${\lambda }_{100}$ and ${\lambda }_{111}$ of trivalent ruthenium ions on octahedral sites in yttrium iron garnet has been calculated in terms of the single-ion model. This leads to simple expressions of the temperature dependence of these quantities which is determined by the exchange field and the ratio of the trigonal field to the spin-orbit coupling. Using these atomic parameters which could be derived from the corresponding anisotropy data a satisfactory fit of the theory to experimental data could be achieved. The measurements of ${\lambda }_{100}$ and ${\lambda }_{111}$ have been carried out on single crystals of the composition ${\mathrm{Y}}_3{\mathrm{Fe}}_{5-x}{\mathrm{Ru}}_x{\mathrm{O}}_{12}$ by means of the resonant method in the temperature range of 4.2-500 K. The contribution of the ${\mathrm{Ru}}^{3+}$ ions turns out to be positive for both ${\lambda }_{100}$ and ${\lambda }_{111}$.