Specific features of Eu 3+ and Tb 3+ magnetooptics in gadolinium-gallium garnet (Gd 3Ga 5O 12)

Abstract

We reported magnetooptical properties of Eu 3+(4f (6)) and Tb 3+(4f (8)) in single crystals of Gd 3Ga 5O 12 (GGG), Y 3Ga 5O 12 (YGG), and Eu 3+(4f (6)) in Eu 3Ga 5O 12 (EuGG) for both ions occupying sites of D 2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb 3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu 3+ in EuGG were studied. The data were obtained at 85 K and room temperature (RT). Magnetic susceptibility of Eu 3+ in EuGG was also measured between 85 K and RT. The magnetooptical and magnetic susceptibility data were modeled using the wavefunctions of the crystal-field split energy (Stark) levels of Eu 3+ and Tb 3+ occupying D 2 sites in the same garnets. The results reported gave a precise determination of these Stark level assignments and confirmed the symmetry labels (irreducible representations) of the closely-spaced Stark levels (quasi-doublets) found in the 5D 1 (Eu 3+) and 5D 4 (Tb 3+) multiplets. Ultraviolet (UV) excitation (<300 nm) of the 6P J and 6I J states of Gd 3+ in the doped GGG crystals led to emission from 5D 4 (Tb 3+) and 5D 1 and 5D 0 (Eu 3+) through radiationless energy transfer to the 4f ( n−1) 5d band of Tb 3+ and to UV quintet states of Eu 3+. The temperature-dependent emission line shapes and line shifts of the magnetooptical transitions excited by UV radiation suggested a novel way to explore energy transfer mechanisms in this rare-earth doped garnet system.