Paramagnetic Resonance of Fe 3 + in Octahedral and Tetrahedral Sites in Yttrium Gallium Garnet (YGaG) and Anisotropy of Yttrium Iron Garnet (YIG)

The electron paramagnetic resonance spectrum of a small ${\mathrm{Fe}}^{3+}$ impurity which enters substitutionally for the gallium in single crystals of yttrium gallium garnet (chemical formula ${\mathrm{Y}}_{3}$${\mathrm{Ga}}_{5}$${\mathrm{O}}_{12}$) has been examined at 24 kMc/sec at 295\ifmmode^\circ\else\textdegree\fi{}K and 1.6\ifmmode^\circ\else\textdegree\fi{}K. ${\mathrm{Fe}}^{3+}$ is studied for the first time in tetrahedral coordination. The results for the crystal field parameters that appear in the usual spin Hamiltonian for ${\mathrm{Fe}}^{3+}$ for the octahedral ($a$) and tetrahedral ($d$) sites are: ${a}_{a}=+0.0185$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${D}_{a}=\ensuremath{-}0.1294$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${F}_{a}=+0.0026$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${a}_{d}=+0.0062$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${D}_{d}=\ensuremath{-}0.0880$ ${\mathrm{cm}}^{\ensuremath{-}1}$, ${F}_{d}=\ensuremath{-}0.0037$ ${\mathrm{cm}}^{\ensuremath{-}1}$.