Strong exchange bias with the (110)-oriented BiFeO3 films

Epitaxial BiFeO3 films were grown on the (001)-, (110)-, and (111)-oriented SrTiO3 substrates. Using CoFe as ferromagnetic layer, we have shown that both large exchange bias and coercive field enhancement can be observed in the (001)- and (110)-oriented BiFeO3. But no exchange bias was found in the (111)-oriented BiFeO3 films, which can be understood by the lack of either 109 degrees or 71 degrees ferroelectric domain walls and the preservation of the spatial modulated cycloid spin structure. The observation of large exchange bias field with the (110)-oriented BiFeO3 film may lead to an alternative choice towards reversible control exchange bias by electrical field. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748160]