Photo-Induced Magnetic Anisotropy of Polymer Film Containing Azobenzene Organic Free Radical Group

The forward degenerate four-wave mixing geometry was employed to induce microstructure in an organic free radical azobenzene polymer film. Before irradiated with Ar⁺ laser beams (λ =514.5 nm), the azobenzene organic free radical polymer exhibits magnetic isotropic measured by superconducting quantum interference device. After photo-induced microstructure, the polymer film becomes magnetic anisotropy. When the applied magnetic field H = 50 Gauss, the magnetization along the normal direction of the polymer film is M_z = 5.5 x 10^-5 emu/g, which is larger than M_x = 4.1 x 10^-5 emu/g in the direction parallel to the polymer film.