The effects of the bonding mechanism and band alignment in a ferroelectric (FE) ${\mathrm{BaTiO}}_3$/ferromagnetic ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnO}}_3$ heterostructure are studied using x-ray photoelectron spectroscopy and first-principles calculations. The band lineup at the interface is determined by a combination of band bending and polarization-induced modification of core-hole screening. A Schottky barrier height for electrons of $1.22\pm 0.17$ eV is obtained in the case of downwards FE polarization of the top layer. The symmetry of the bonding states is emphasized by integrating the local density of states $\pm 0.2$ eV around the Fermi level, and strong dependence on the FE polarization is found: upwards, polarization stabilizes Ti $t_{2g}\left(xy\right)$ orbitals, while downwards, polarization favors Ti $t_{2g}\left(yz\right)$ symmetry. It is predicted that the abrupt $(\text{La},\text{Sr})|{\mathrm{TiO}}_2$ interface is magnetoelectrically active, leading to a A-type antiferromagnetic coupling of the first ${\mathrm{TiO}}_2$ interface layer with the underlying manganite layer through a superexchange mechanism.

• Received 13 August 2015

DOI:https://doi.org/10.1103/PhysRevB.92.235442