Linear and non-linear magneto-optical studies of Pt/Co/Pt thin films

Linear magneto-optical Kerr effect (MOKE) microscopy and magnetization-induced second-harmonic-generation (MSHG) magnetometry and imaging were used as two complementary optical techniques to measure the magnetic hysteresis loops and to visualize the domain structure in Pt/Co/Pt thin films with a weak uniaxial in-plane magnetic anisotropy. While the MOKE is used to probe the magnetization over the full thickness of the Co layer, MSHG is used to check the Co/Pt interfaces selectively. When the magnetic field H is not applied along the easy axis a, longitudinal MOKE and MSHG hysteresis loops exhibit different shapes. The differences between the longitudinal MOKE and MSHG magnetic pattern images for H parallel to a are only found in domain wall regions. All of these results are interpreted by considering transverse components of the non-linear optical polarization.