Memory effects of exchange coupling in ferromagnet/antiferromagnet bilayers

The magnetization state of the ferromagnet is crucial in the cooling process for establishing exchange coupling in ferromagnet/antiferromagnet bilayers. Using specialll cooling procedures, the value and even the sign of the exchange bias field in several bilayers can be greatly altered. While the coercivity only depends on temperature, the exchange bias field shows an accumulative memory of the thermal and field history of the bilayer. We propose that this is due to the formation of a domain wall with a temperature dependent width in the antiferromagnet.