Magnetic Susceptibility and Crystalline Field Levels of Ytterbium Gallium Garnet

Abstract

The paramagnetic susceptibility of YbGaG is measured over the interval 4-1000\ifmmode^\circ\else\textdegree\fi{}K, primarily in order to obtain information on the location of the ${\ensuremath{\Gamma}}_{6}$ level, which, unlike ${\ensuremath{\Gamma}}_{8}$, does not combine magnetically with the ground ${\ensuremath{\Gamma}}_{7}$ state, and so is not detectable in the usual magnetic experiments at low temperatures. From our measurements it is inferred that the ${\ensuremath{\Gamma}}_{6}$ level is about 800 ${\mathrm{cm}}^{\ensuremath{-}1}$ above ${\ensuremath{\Gamma}}_{7}$. High precision cannot be claimed for this estimate, as our analysis of the magnetic data is made on the assumption of a perfectly cubic crystalline field, whereas the local symmetry at an individual lattice site is known to be but approximately cubic. In any case, the conclusion seems warranted that any low-lying levels at 100 ${\mathrm{cm}}^{\ensuremath{-}1}$ or so deduced from optical absorption data are of a vibrational rather than electronic nature.