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. Result s showed that the exchange coupling effects, i.e. unidirectional anisotropy field, H-s (shift of the hysteresis loop), and broadening of the hysteresi s 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 observ ed between as deposited and field cooled bilayers. Practically no contracti on of the successive hysteresis loops (training effects) was also observed at room temperature. On the other hand, the interface exchange coupling eff ects strongly depend on the preparation conditions. A maximal coupling ener gy for the NiO-Co interface was estimated as 0.04 mJ/m(2) at room temperatu re for the samples prepared onto SiO2(101)/Si(100) substrates.