Oscillatory behavior of perpendicular magnetic anisotropy in Pt/Co/Al(Ox) films as a function of Al thickness

The evolution of the perpendicular magnetic anisotropy of Pt/Co/AlOx structures has been followed by extraordinary Hall Effect measurements as a function of both Al thickness and annealing treatment. A nonmonotonous evolution of the magnetic anisotropy is observed with increasing aluminum thickness, with a maximum around 1.4 nm attributed to the formation of quantum well states in the remaining metallic Al layer. This maximum gradually disappears after annealing. High resolution electron microscopy images indicate that the vanishing of this maximum is associated with homogenization of oxygen throughout the whole Al layer.