Nanoscale control of exchange bias with BiFeO3 thin films.

Martin, Lane W; Chu, Ying-Hao; Holcomb, Mikel B; Huijben, Mark; Yu, Pu; Han, Shu-Jen; Lee, Donkoun; Wang, Shan X et al. · Nano Lett · 2008

basic_science · Level V

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Abstract

We demonstrate a direct correlation between the domain structure of multiferroic BiFeO3 thin films and exchange bias of Co 0.9Fe 0.1/BiFeO3 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 ( approximately 2 nm) domain walls in the BiFeO3 film. We show that the magnitude of the exchange bias interaction scales with the length of 109 degrees ferroelectric domain walls in the BiFeO 3 thin films which have been probed via piezoresponse force microscopy and X-ray magnetic circular dichroism.