Nanoscale control of exchange bias with BiFeO 3 thin films

We demonstrate a direct correlation between the domain structure of multiferroic BiFeO 3 thin films and exchange bias of Co 0.9Fe 0.1/BiFeO 3 heterostructures. Two distinct types of interactions - an enhancement of the coercive field (exchange enhancement) and an enhancement of the coercive field combined with large shifts of the hysteresis loop (exchange bias) - have been observed in these heterostructures, which depend directly on the type and crystallography of the nanoscale (∼2 nm) domain walls in the BiFeO 3 film. We show that the magnitude of the exchange bias interaction scales with the length of 109° ferroelectric domain walls in the BiFeO 3 thin films which have been probed via piezoresponse force microscopy and X-ray magnetic circular dichroism. © 2008 American Chemical Society.