Nonlinear Magneto-Optical Properties of Sputtered and Epitaxial Ultrathin Films

The nonlinear magneto-optical properties of polycrystalline Co films and single crystalline Fe films epitaxially grown on Co(001) substrate are studied ex situ and in situ, respectively, by the magnetization-induced second harmonic generation (MSHG) technique. The magnetic contrast in MSHG intensity can be clearly distinguished for the cobalt films, and dependence of the magnetic second harmonic intensity on the thickness of the magnetic film and a nonmagnetic covering is found, which is the result of the combined contributions of the magnetic surface and interfaces. A giant nonlinear Kerr rotation of more than 2 degrees, being at least an order of magnitude larger than its linear one, is achieved for the polycrystalline Co films. By using the MSHG method, the magnetic phase transitions of the ultrathin epitaxial Fe films at a thickness of about 4 ML and 11 ML can be successfully observed, showing sensitivity to the film structure and magnetic orders. If combined with the magneto-optical Kerr effect.