Memory effects of exchange coupling in ferromagnet/antiferromagnet bilayers

The magnetization state of the ferromagnet is crucial in the cooling proces s for establishing exchange coupling in ferromagnet/antiferromagnet bilayer s. Using special cooling procedures, the value and even the sign of the exc hange bias field in several bilayers can be greatly altered. While the coer civity only depends on temperature, the exchange bias field shows an accumu lative memory of the thermal and field history of the bilayer. We propose t hat this is due to the formation of a domain wall with a temperature depend ent width in the antiferromagnet. [S0163-1829(99)02130-X].