Cubic and quadratic nonlinear magneto-optical Kerr effect in magnetic nanogranular films

We present the results of the experimental studies of nonlinear-optical and nonlinear magneto-optical properties of granular magnetic films exhibiting giant magnetoresistance effect. The samples under study are Co-containing nanogranular films of the composition ( Co ) x ( Al 2 O 3 ) 1-x , the concentration of cobalt, x , being varied in a wide range. A strong azimuthal anisotropy in the intensity of the second (SHG) and third harmonics (THG) is observed which proves the anisotropic crystallographic structure of granular films. The nonlinear magneto-optical Kerr effect (NOMOKE) in SHG and THG is studied in the films for the geometry of the transversal magnetization. The dependence of the NOMOKE contrast in the SHG (THG) intensity is found to be a non-monotonous function of Co content in the films. The dependence of the magnetization-induced components of the quadratic susceptibility on the content of Co in the films is estimated.