Investigation of Metallic/Oxide Interfaces in Pt/Co/AlO $_{\rm x}$ Trilayers by Hard X-Ray Reflectivity

X-ray reflectivity (XRR) is used to determine the oxidation front at the nanometer scale in sputtered perpendicular semi tunnel junctions, as the form Pt/Co/AlO x , by varying the oxidation time t Ox of the capping layer. From XRR simulations, we show that the nature of the stack is gradually defined according to the value of t Ox . For low t Ox values ( x multilayer is appearing whereas a Pt/Co/CoO/AlO x architecture takes place for higher t Ox . The oxygen-induced magnetic properties obtained by extraordinary Hall effects measurements are explained by the structural results. The increase of Co-O bondings with t Ox is at the origin of the appearing of the perpendicular magnetic anisotropy (PMA).