Exchange anisotropy in NiO/Co bilayers

40 nm-NiO/d(Co)-Co bilayers (0 < d(Co) < 40 nm) were prepared onto SiO2(101)/Si(100) and glass substrates using UHV RF/DC magnetron sputtering. Results showed that the exchange coupling effects, i.e. unidirectional anisotropy field, H-s (shift of the hysteresis loop), and broadening of the hysteresis loop, DeltaH(c), are inversely proportional to the Co thickness down to 2 nm. Furthermore, no significant difference in H-s and DeltaH(c) was observed between as deposited and field cooled bilayers. Practically no contraction of the successive hysteresis loops (training effects) was also observed at room temperature. On the other hand, the interface exchange coupling effects strongly depend on the preparation conditions. A maximal coupling energy for the NiO-Co interface was estimated as 0.04 mJ/m(2) at room temperature for the samples prepared onto SiO2(101)/Si(100) substrates.