Optical and magnetooptical properties of terbium-scandium-aluminum and terbium-containing (gallates and aluminates) garnets

Comparative measurements of the Faraday rotation in Tb3Ga5O12 (TGG) and Tb3Sc2-xAl3+хO12 (TSAG) garnets shows the values of the Verdet constant for TSAG are about 25% higher than that of TGG in the wavelength range 400-700 nm at the temperatures T=95 and 300 K. The increase of the Verdet constant is explained by increase of the “paramagnetic” frequency factor caused by the shift of the resonance frequency of the first allowed 4f→5d transition to the area of the lower frequencies in UV. The shift and observed strong broadening of the UV absorption bands in TSAG are explained by significant modification of the crystalline environment of the Tb3+ ion in this garnet. A comparison of the data of the C/D ratio in TSAG with the value of the magnetic moment of the Tb3+ ground state in Tb3Al5O12 (TAG) determined from magnetic measurements, showed an acceptable agreement for these parameters measured by fundamentally different methods. Measurements of the visible emission spectra reveal a strong influence of some disordering of the crystal field (CF) in TSAG in comparison with the terbium-aluminum garnet spectra. Magnetooptical effects of the intensity change of the luminescence lines in TSAG is caused by modification of the electronic structure of the 5D4 and 7F5 multiplets by Sc3+ ions in the lattice, leading to a local symmetry reduction of the Tb3+ ion in TSAG.