Magnetoelectric coupling at the interface of BiFeO3/La0.7Sr0.3MnO3 multilayers

Electric-field controlled exchange bias in a heterostructure composed of the ferromagnetic manganite La0.7Sr0.3MO3 and the ferroelectric antiferromagnetic BiFeO3 has recently been demonstrated experimentally. By means of a model Hamiltonian, we provide a possible explanation for the origin of this magnetoelectric coupling. We find, in agreement with experimental results, a net ferromagnetic moment at the BiFeO3 interface. The induced ferromagnetic moment is the result of the competition between the e(g)-electron double exchange and the t(2g)-spin antiferromagnetic superexchange that dominates in bulk BiFeO3. The balance of these simultaneous ferromagnetic and antiferromagnetic tendencies is strongly affected by the interfacial electronic charge density, which, in turn, can be controlled by the BiFeO3 ferroelectric polarization.