Determination of Oxidation States in Magnetic Multilayers

X-ray photoelectron spectroscopy has been used to characterize the oxidation states in Ta/NiO_x/Ni₈₁Fe₁₉/Ta magnetic multilayers prepared by rf reaction and dc magnetron sputtering. The exchange coupling field and the coercivity of NiO_x/Ni₈₁Fe₁₉ are studied as a function of the ratio of Ar to O₂ during the deposition process. The chemical states of Ni atoms in the interface region of NiO_x/NiFe were also investigated by XPS and the peak decomposition technique. The results show that the ratio of Ar to O₂ has a great effect on the chemical states of nickel in NiO_x films. Thus the exchange coupling field and the coercivity of Ta/NiO_x/Ni₈₁Fe₁₉/Ta are affected seriously. Also, the experiment shows that XPS is a powerful tool in characterizing magnetic multilayers.