Direct evidence of controlling the population of magnetic domains in BiFeO${}_3$ thin films through electric field is reported using neutron diffraction. By fabricating BiFeO${}_3$ thin films on vicinal SrTiO${}_3$ substrates, we have achieved ferroelectric monodomains as confirmed by piezoresponse force microscopy. The application of an electric field between the bottom SrRuO${}_3$ and the top electrode switches the ferroelectric domain state with concomitant changes in magnetic reflections observed with neutron diffraction, indicating changes in the antiferromagnetic domain populations. The observed magnetoelectric switching behavior by neutron diffraction is compared with the electric-field effect on the magneto-optical Kerr effect measurement on patterned pads of exchange coupled Co film deposited on top of the BiFeO${}_3$ films. The present result shows possible new directions for the realization of magnetoelectric devices.

• Received 10 October 2012

DOI:https://doi.org/10.1103/PhysRevB.87.140405