Enhanced magneto-optical Kerr effect in oxidized Co thin films

We have studied the structural and magneto-optical properties of postdeposition oxidized Co thin films. The oxidization process leads to the formation of a double-layered structure of fcc Co3O4 on top of metallic Co. The magneto-optical Kerr effect (MOKE), measured in the range 0.8 eV⩽EPh⩽5.5 eV reveals characteristic dependencies of the MOKE spectra on annealing temperature and time. In particular, we observe resonance-type enhancements of the Kerr effects by up to a factor of 10 compared with unannealed metallic Co. The experimental data are quantitatively reproduced by bilayer optical stack calculations.