Multiferroic oxide heterostructures

Magnetoelectric coupling at the interface of BiFeO3/La0.7Sr0.3MnO3 multilayers.
M.J. Calderon, S. Liang, R. Yu, J. Salafranca, S. Dong, S. Yunoki,L. Brey, A. Moreo, and E. Dagotto arXiv:1012.1448.

Electric-field controlled exchange bias in a heterostructure composed of the ferromagnetic manganite La0.7Sr0.3MnO3 and the ferroelectric antiferromagnetic BiFeO3 has recently been demonstrated experimentally[1]. By means of a microscopic model Hamiltonian we provide a possible explanation of 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 eg-electrons double exchange and the t2g-spins antiferromagnetic superexchange that dominate 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.
[1] S. M. Wu et al., Nat. Mat. 9, 756 (2010); P. Yu et al., Phys. Rev. Lett. 105, 027201 (2010).

EB
Magnetization induced in BiFeO3 (MBFO) as a function of JAFM and V0 for (a)Voffset = 0 and (b) Voffset = 0.6t.(c) Electronic charge in the heterostructure for V0= -0.5t and V0= 0.5t. Inset: charge at the interfacial BiFeO3 layer for -1t < V0 < 1t. t is the hopping parameter and the energy unit. V0 is an attractive or repulsive potential arising in the interfacial BiFeO3 layer as a result of the ferroelectric polarization in BiFeO3. Voffset is the band offset between La0.7Sr0.3MnO3 and BiFeO3