The remagnetization experiment of the bilayer in the hard direction supports the correctness of the assumption that the anisotropy distribution in the AF layer is inhomogeneous. As one can see from Fig. 3(c), when the field is decreased, the inhomogeneous rotation of MS is determined by the dislocations. More detailed analysis shows that the spins rotate at lower fields near these dislocations. Only when the field is switched to zero will all the spins orient along the unidirectional anisotropy axis [Fig. 3(d)].
In summary, we have studied experimentally the magnetization reversal of epitaxial NiO/NiFe bilayers. We have extended the model of exchange biasing[11] to describe the measured enhanced coercivity and asymmetry observed in these bilayers in the activity of various domain nucleation centers.
The Russian co-workers gratefully acknowledge a research grant from the Russian Foundation for Basic Research No. 97-02-16879.