Spectroscopic Study of the Ytterbium-Iron Exchange Interaction in Ytterbium Iron Garnet

The exchange splittings of the ytterbium ground-state doublet and of an excited state ($J=\frac{5}{2}$) doublet have been determined from spectroscopic studies of single-crystalline, ytterbium-iron garnet. The splittings were observed at 77°K as a function of the orientation of the magnetization of the crystal. The splittings exhibit the functional form of the $g$ tensor of a two-level system. The principal values of the splittings (referred to local $x$, $y$, $z$ axes) are, for the ground state doublet, 11.6, 25.7, and 29.9 ${\mathrm{cm}}^{-1\mathrm{}}$ and, for the excited state doublet, 15.9, 5.8, and 29.9 ${\mathrm{cm}}^{-1\mathrm{}}$.