Birefringence-mediated enhancement of the magneto-optical activity in anisotropic magnetic crystals

Optical anisotropy is usually treated as an unfavorable condition for the magneto-optical measurements since it is known to diminish the Faraday rotation concerning the case of the isotropic medium. Here we show that the situation could be quite opposite: a phenomenon of birefringence mediated enhancement of the magneto-optical activity appears if the incident light polarization and angle of incidence are set properly. The present study relies on the experimental, analytical, and numerical studies of iron borate $\mathrm{FeBO_3}$ crystals. We demonstrate a significant increase of the magneto-optical activity resulting in nearly $100\%$ magneto-optical light modulation magnitude. The approach applies to other types of birefringent crystals with the magneto-optical response that makes it crucial for various practical applications, including magneto-optical microscopy, pump-probe studies, and others.