Oxygen adsorption and magnetic properties of ultrathin Co/Ir(111) films

During oxygen exposure to ultrathin Co/Ir(111) films, both the oxidative process and physical adsorption occur. The diffusion length of oxygen is around two monolayers of Co. Within this thickness, Co films are almost oxidative and ferromagnetism disappears. For thicker films with nanometer thickness, after completing the oxidative process at the beginning of oxygen exposure, the physical adsorption becomes a major process. By controlling the amount of further exposure to oxygen, the coercive force in the polar configuration can be adjusted while keeping the Kerr rotation at a nearly constant value.