Observation of a Transversal Nonlinear Magneto-Optical Effect in Thin Magnetic Garnet Films

A simultaneous breaking of space and time-reversal symmetry leads to a coexistence of crystallographic ${\chi }_{\mathrm{ijk}}^{\left(2\right)}\left(2\omega \right)$ and magnetization-induced ${\chi }_{\mathrm{ijkl}}^{\left(3\right)}\left(2\omega \right)$ electric-dipole type contributions to the nonlinear optical susceptibility in the same medium. As a consequence, a new transversal nonlinear magneto-optical effect arises that is linear in M. This effect is experimentally demonstrated in thin films of magnetic garnets, as well as large effects quadratic in M. We suggest a novel method to distinguish the two susceptibility contributions based on their different transformation properties.