Quadratic effects in the nonlinear magneto-optical response of perovskite manganites studied with magnetization-induced second harmonic generation

The crystallographic and magnetic symmetry of centrosymmetric perovskite manganite epitaxial films is studied by magnetization-induced optical second harmonic generation (MSHG). It is shown that not only linear but also quadratic terms in the magnetization affect the nonlinear-optical response, the latter being even dominant for special geometries. In that case MSHG allows to simultaneously probe the crystallographic structure, the net magnetization (zero in demagnetized material), and magnetization squared (nonzero in demagnetized material).