Ferromagnetic Resonance in Ruthenium-Doped Gadolinium Iron Garnet

Abstract

Ferromagnetic-resonance measurements on single crystals of gadolinium iron garnet doped with ruthenium were carried out at 9.25 GHz in the temperature range 4.2-500 \ifmmode^\circ\else\textdegree\fi{}K. The single-ion model is used to calculate the anisotropy contributions $\ensuremath{\Delta}{K}_{1}$ and $\ensuremath{\Delta}{K}_{2}$ and the field for ferromagnetic resonance. By fitting the theory to the experimental anisotropy data one finds $g{H}_{e}=1.2\ifmmode\times\else\texttimes\fi{}{10}^{7}$ Oe and $\frac{v}{\ensuremath{\xi}}=\ensuremath{-}0.4$, where $g$, ${H}_{e}$, $v$, and $\ensuremath{\xi}$ are the $g$ factor, the exchange field, the one-electron trigonal-field parameter, and the one-electron spin-orbit-coupling parameter, respectively. The linewidth could be interpreted in terms of the longitudinal-relaxation model assigning a short relaxation time of $\ensuremath{\tau}=3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ sec to the ${\mathrm{Ru}}^{3+}$ ions.