Magnetic properties of ultrathin Si/Co/Ir(111) films

A magnetic phase diagram for Si/Co/Ir(111) films has been established by the surface magneto-optic Kerr effect technique. The Si coverage, where ferromagnetism vanishes, increases from one monolayer to more than three monolayers as the coverage of the Co layer increases from two to five monolayers. As silicon is deposited on the surface of Co/Ir(111) films, Si atoms interact with the Co layer to form Si-Co compounds. The rough Si/Co interface impedes the motion of domain walls during the magnetization reversal process, thus increasing the coercive force. The formation of nonmagnetic Co-Si compounds reduces the effective magnetic layers, leading to a decrease in Kerr intensity and superparamagnetic behavior of the films.