The magneto-optical Kerr effect enhancement in Co_xAg_1-x granular films

The magneto-optical Kerr effect enhancement in Co_xAg_1-x granular magnetic films annealed at 100, 250, 400, 500 °C was studied. The optical constants, the complex dielectric function and magneto-optical Kerr parameters were measured at room temperature. For the sample Co₂Ag₉₈, strong Kerr effect enhancement is observed around the Ag plasma edge. With increasing annealing temperature, the values of the Kerr rotation θ_K and Kerr ellipticity εK increase, resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. As the Co composition x increases the Kerr effect enhancement is weakened and disappears for x > 50%. From the analysis of the experimental data, it is concluded that the magneto-optical Kerr effect enhancement is due to the presence of the steep plasma edge.