Magnetism and magneto-optical response from ultra-thin Co films epitaxially grown on Pd substrates

Magnetism of ultrathin Co films grown on clean and atomically flat surfaces of Pd single crystals is investigated using the magneto-optical Kerr effect (MOKE). The film deposited at room temperature exhibits a perpendicular magnetic anisotropy (PMA) after an exposure to a residual atmosphere at low temperatures (70 K) most likely due to hydrogen adsorption. MOKE analysis shows a gradual appearance of PMA and indicates the rotation of the magnetization vector from the sample plane. Upon increasing the temperature, the magnetization vector rotates back to the plane for temperatures approaching 200 K. Annealing above room temperature also supports PMA of the Co films on Pd substrates. The polar MOKE loops change sign at a certain critical thickness, t_c, which varies for different substrate planes and growth conditions. The reversed loops are a property of the Co/Pd interface, even for samples grown at room temperature only.