Magnetic Susceptibility and Crystalline Field Levels of Ytterbium Gallium Garnet

The paramagnetic susceptibility of YbGaG is measured over the interval 4-1000^∘{}K, primarily in order to obtain information on the location of the Γ₆ level, which, unlike Γ₈, does not combine magnetically with the ground Γ₇ state, and so is not detectable in the usual magnetic experiments at low temperatures. From our measurements it is inferred that the Γ₆ level is about 800 cm^-1 above Γ₇. 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 cm^-1 or so deduced from optical absorption data are of a vibrational rather than electronic nature.