Competing interfacial exchange and Zeeman energies in exchange biased bilayers

The exchange bias in antiferromagnet (MnF2)/ferromagnet (Fe) bilayers has b een studied as a function of temperature, cooling field, and interfacial ro ughness. Positive exchange bias is observed under certain conditions, along with a nonmonotonic roughness dependence. The unusual cooling field depend ence can be understood within a simple model in which the exchange bias is determined by a competition between a roughness-dependent average exchange energy and a Zeeman energy for the antiferromagnet surface spins. Our resul ts are consistent with the existence of a domain wall parallel to the inter face in the Fe layer, contrary to earlier theoretical models. [S0163-1829(9 9)08541-0].