Direct observations of ferromagnetic and antiferromagnetic domains in Pt/Co/Cr₂O₃/Pt perpendicular exchange biased film

By using focused soft X-rays, magnetic domain imaging based on X-ray magnetic circular dichroism (XMCD) measurements was performed on a Pt/Co/Cr2O3/Pt film that exhibits both perpendicular magnetic anisotropy and perpendicular exchange anisotropy. In the AC-demagnetized state, spatial distributions of the XMCD corresponding to the magnetic domains were clearly observed. In particular, ferromagnetic and antiferromagnetic magnetic domains were separately observed by tuning the photon energy to either the ferromagnetic Co L₃ edge or the antiferromagnetic Cr L₃ edge. The ferromagnetic domain pattern is similar to the ones previously reported for Co/Pt multilayers, and the ferromagnetic and antiferromagnetic domains are spatially coupled. The magnetization curve measured after cooling the sample, while maintaining the demagnetized state, exhibited positive and negative exchange biases simultaneously, which suggests that the exchange bias is determined on a domain-by-domain basis.