Magnetic structure of epitaxial multiferroic BiFeO3 films with engineered ferroelectric domains

We report on neutron scattering and piezoresponse force microscopy studies of multiferroic BiFeO3 films epitaxially grown on vicinal SrTiO3 substrates. We find that these BiFeO3 films exhibit a G-type antiferromagnetic structure modulated with cycloidal spiral magnetic ordering with the features of magnetic domains depending upon the ferroelectric domain states: a single antiferromagnetic domain for the films with a ferroelectric monodomain while two- or multiantiferromagnetic domains existing in the films displaying two- or four-ferroelectric variants, respectively. These results imply the correlation between ferroelectric and magnetic order parameters in the BiFeO3 films and the expected strong magnetoelectric coupling makes these multiferroic films promising candidates for device applications with the capability to tune the magnetism using an electric field.