Ta/NiO/NiFe/Ta multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (Hex) between NiO and NiFe reached 120Oe. The composition 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 = 3Ni+Fe2O3. The thickness of the chemical reaction as estimated by angle-resolved XPS was about 1-1.5nm. These interface reaction products are magnetic defects, and we believe that the Hex and the coercivity (Hc) of NiO/NiFe are affected by these defects. Moreover, the results also show that there is an “intermixing layer” at the Ta/NiO (and NiO/Ta) interface due to a thermodynamically favorable reaction: 2Ta+5NiO=5Ni+ Ta2O5. This interface reaction has an effect on the exchange coupling as well. The thickness of the “intermixing layer” as estimated by XPS depth-profiles was about 8-10nm. The exchange coupling field (Hex) between NiO and NiFe reached 120Oe. The composition 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 = 3Ni + Fe2O3. The thickness of the chemical reaction as estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products are magnetic defects, and we believe that the Hex and the coercivity (Hc) of NiO / NiFe are affected by these defects. Moreover, the results also show that there is an “intermixing layer” at the Ta / NiO (and NiO / Ta) interface due to a thermodynamically favorable reaction: 2Ta + 5NiO = 5Ni + Ta2O5. This interface reaction has an effect on the exchange coupling as well. thickness of the “intermixing layer ” as es timated by XPS depth-profiles was about 8-10nm.