Exchange Coupling in NiO/Ni Double Layer Films

NiO/Ni double layer films were prepared by partial oxidation of Ni films deposited on MgO(100) substrates by a vacuum evaporation method, and the exchange coupling field H ex and the easy coercive force H ce in the films were studied in relation to the substrate temperature T s and the oxidation temperature. As a result, it is found that (1) Ni films deposited at low T s (100° C) are easily oxidized at low temperatures (∼450° C), compared with those deposited at higher T s (200° C or 300° C), (2) H ex and H ce in NiO/Ni double layer films prepared at low temperatures are large compared with those in films prepared at high temperatures. The reasons for the increase of H ex and H ce in NiO/Ni films prepared at low temperatures are discussed.