The Faraday rotation of TbFe₃(BO₃)₄${\mathrm{TbFe}}_3{({\mathrm{BO}}_3)}_4$ is determined by the Tb³⁺ subsystem at T<T_N$T<T_N$.

The magneto-optical constant A   in TbFe₃(BO₃)₄${\mathrm{TbFe}}_3{({\mathrm{BO}}_3)}_4$ depends on temperature.

This magneto-optical constant A has a magnetic contribution.

The magneto-optical constant A′$A\prime$ in TbFe₃(BO₃)₄${\mathrm{TbFe}}_3{({\mathrm{BO}}_3)}_4$ is temperature independent.