XPS Studies of Chemical States of NiO/NiFe Interface

Ta/NTiO/NiFe/Ta multilayers were prepared by radio frequency reactive and dc magnetron sputtering. The exchange coupling field between NiO and NiFe reached 9.6 × 10³ A/m. The compositions and chemical states at the interface region of NiO/NiFe were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique, The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe = Ni + FeO and 3NiO+2Fe =3 Ni+Fe₂O₃. The thickness of the chemical reaction area estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products appear magnetic defects, and the exchange coupling field H_ex and the coereivity H_c of NiO/NiFe are affected by these defects.