Magnetic circular dichroism and optical absorption spectra of Eu3+ in Y3Al5O12(YAG)

Abstract

Magnetic circular dichroism (MCD) and optical absorption spectra of Eu³⁺ in the rare-earth garnet Y₃Al₅O₁₂(YAG) have been recorded between 4600 and 36 000 cm^–1 at 77 K and at room temperature. A total of 138 crystal-field transitions has been detected in the spectra. The symmetry of the Eu³⁺ site is D₂, so that a total removal of the crystal-field degeneracy of the 4f⁶ configuration can be expected. Special attention is given to the complementarity of MCD and absorption spectroscopy. Spectral bands which are not resolved in the absorption spectra are often resolved in the MCD spectra. This complementarity is especially advantageous for the reconstruction of the crystal-field splitting pattern of the ⁵D₁ and ⁵L₆ manifolds. The energy level scheme of Eu³⁺ in YAG is parametrized in terms of 20 free-ion parameters and nine crystal-field parameters. The crystal field is strong in the garnet host, so that J-mixing has to be taken into account for the crystal field calculation. Because of the importance of J-mixing, 4f–4f transitions not obeying the Judd–Ofelt selection rules for induced electric dipole transitions are observed in the spectra.