Hyperfine Interactions in Europium Iron Garnet

The temperature dependence of the hyperfine fields at the ${\mathrm{Eu}}^{151}$ nuclei in europium iron garnet (EuIG) has been measured by the Mössbauer effect. The magnetic hyperfine fields at the two magnetically inequivalent Eu sites are 630±5 and 570±5 kOe, respectively, extrapolated to 0°K. The ratio of the $g$ factor of the 22-keV excited state to that of the ground state is $\frac{g_{22}}{g_g}=0.5332\mathrm{}\left(5\right)\mathrm{}$, and that of the spectroscopic quadrupole moments is $\frac{Q_{22}}{Q_g}=1.28\mathrm{}\left(4\right)\mathrm{}$.