Magnetization reversal of uncompensated Fe moments in exchange biased Ni/FeF2 bilayers

The magnetization reversal of uncompensated Fe moments in exchange biased Ni/FeF2 bilayers was determined using soft x-ray magnetic circular and linear dichroism. The hysteresis loops resulting from the Fe moments are almost identical to those of the ferromagnetic Ni layer. However, a vertical loop shift indicates that some Fe moments are pinned in the antiferromagnetically ordered FeF2. The pinned moments are oriented antiparallel to small cooling fields, leading to negative exchange bias, but parallel to large cooling fields, resulting in positive exchange bias. No indication for the formation of a parallel antiferromagnetic domain wall in the FeF2 layer upon magnetization reversal in the Ni layer was found