Specific Features of ${\hbox{Tb}}{^{3+}}$ Magnetooptics in Terbium Iron and Terbium Gallium Garnets (${\hbox{Tb}}_{3}{\hbox{Fe}}_{5}{{\hbox{O}}_{12}}$ and ${\hbox{Tb}}_{3}{\rm Ga}_{5}{{\hbox{O}}_{12}}$ )

We reported magnetooptical properties of Tb
³⁺
in single crystals of Tb
₃
Fe
₅
O
₁₂
and Tb
₃
Ga
₅
O
₁₂
for ion occupying sites of D
₂
symmetry in the garnets structure. It is shown that in the employed Voigt geometry the magnetic linear birefringence and the dichroism reach values 10
^-4
, and have a strong dependence on the wavelength and a strong anisotropy. The absorption spectra were obtained at temperatures of 30 K, 82 K, 100 K using magnetic field up to 25 kOe applied parallel and perpendicular to the electric vector E linearly polarized light on the
⁷
F
₆
-
⁷
F
₀
and
⁷
F
₆
-
⁷
F
₁
optical transitions region. The aim of this research was revealing of a role of contributions of exchange interaction and a crystal field in splitting of energy levels of the basic condition
⁷
F
₆
ion Tb
³⁺
multiplet in Tb ferrite-garnet by studying of character of spectra of magnetic linear dichroism (MLD) paramagnetic and ferrimagnetic crystals placed in an external magnetic field. Moreover, the assumption about nonreciprocity of magnetic linear birefringence (MLB) spectra and dichroism with the change of the relative orientation of the magnetization vector I and the light wave vector has been experimentally confirmed. This effect may be used as a base for the design of the different transducers, for example, magnetooptical optical channels commutator.