A polymer containing azobenzene side groups each with an organic free radical end was synthesized. Before irradiation by an Ar+ laser beam, the polymer was magnetically isotropic. However, with the irradiation of a polarized Ar+ laser beam, the photoisomerization and reorientation of the azobenzenes took place bringing about a magnetic anisotropy in the radical containing polymer film. The magnetic anisotropy was studied by using a superconducting quantum interference device. It was found that when the applied magnetic field H≈1 Oe, the magnetization Mz(H) in the direction perpendicular to the polymer film was 3.63×10-4 emu/g, while those parallel to the polymer film were Mx(H)=My(H)=-1.1×10-5 emu/g. © 2003 American Institute of Physics.