Magnetic-field switching of second-harmonic generation in noncentrosymmetric magnet Eu2MnSi2O7

We report a giant magnetic-field effect on optical second-harmonic generation (SHG) in a noncentrosymmetric ferrimagnet ${\mathrm{Eu}}_{2}\mathrm{Mn}{\mathrm{Si}}_{2}{\mathrm{O}}_{7}$. The SHG intensity changes at visible photon energy of 2.8 eV by more than 7000% upon the reversal of magnetic-field direction. Such pronounced modulation of the nonlinear optical activity results from an interference between crystallographic and magnetically induced nonlinear polarization. The amplitude of these nonlinear optical susceptibilities is controlled by the spin alignment and the light incident angle, enabling to optimize the magnetic switching of SHG in detail.