The electron paramagnetic resonance spectra of Yb3+ ions in the optically bistable compound, Yb:CsCdBr3, were presented. The observed features were attributed to symmetrically coupled pair complexes of the form, Yb3+-vCd-Yb3+ (vCd = Cd vacancy), with their axis parallel to the crystallographic c-axis. There were no asymmetrical pairs of the type, Yb3+-Yb3+-vCd. It was shown that simulation of the spectra was possible only when an exchange interaction was taken into account in the spin Hamiltonian. A value of J = -0.0016/cm showed that the exchange interaction was antiferromagnetic, but extremely weak. It was also found that there was a significant relaxation (about 12%) of the Yb3+ ions towards the Cd vacancy. From the experimental g-tensor values, it was deduced that the lower ground state of the Yb3+ ions comprised mainly 4fφ (63%) and 4fδ (32%) Yb orbitals. It had previously been proposed that the optical bistability was due to asymmetrical pairs of the type, Yb3+-Yb3+-vCd. On the basis of this work, that was now concluded to be unlikely.

Ytterbium-Ion pairs in Yb:CsCdBr3 - Ion-Ion Interaction and the Electronic Ground State Investigated by Electron Paramagnetic Resonance Spectroscopy. V.Mehta, D.Gourier: Journal of Physics - Condensed Matter, 2001, 13[20], 4567-78