XPS Studies of Magnetic Multilayers

NiO_x/Ni₈₁Fe₁₉ and Co/AlO_x/Co magnetic multilayers were fabricated by reactive RF/DC magnetron sputtering on clean glass substrates and oxidized Si (100) substrates, respectively. The exchange biasing field (H_ex) between NiO_x and Ni₈₁Fe₁₉ as a function of NiO_x oxidation states was studied by X-ray photoelectron spectroscopy (XPS). The oxidation states and the oxide thickness of Al layers in magnetic multilayer films consisting of Co/AlO_x/Co were also analyzed. It is found that the H_ex of NiO_x/Ni₈₁Fe₁₉ films only depends on Ni²⁺ but not on Ni³⁺ or Ni. The bottom Co can be completely covered by depositing an Al layer thicker than 2.0 nm. The oxide layer was Al₂O₃, and its thickness was 1.15 mn.