Interface reaction of Ta/NiO and its effect on exchange coupling

Ta/NiO/NiFe/Ta multilayers, utilizing Ta as the buffer layer, were prepared by RF reactive and DC magnetron sputtering. The exchange coupling field between NiO and NiFe reached a maximum value of 120 Oe at a NiO film thickness of 50 nm. The composition and chemical state at the interface region of Ta/NiO/Ta were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results 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. The thickness of the 'intermixing layer' as estimated by XPS depth-profiles was about 8-10 nm. (C) 2001 Elsevier Science B.V. All rights reserved.