Influence of hole depletion and depolarizing field on the BaTiO3/La0.6Sr0.4MnO3 interface electronic structure revealed by photoelectron spectroscopy and first-principles calculations

Abstract : The effects of the bonding mechanism and band alignment in a ferroelectric (FE) BaTiO3/ferromagnetic La0.6Sr0.4MnO3 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 ± 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 ±0.2 eV around the Fermi level, and strong dependence on the FE polarization is found: upwards, polarization stabilizes Ti t2g(xy) orbitals, while downwards, polarization favors Ti t2g(yz) symmetry. It is predicted that the abrupt (La,Sr)|TiO2 interface is magnetoelectrically active, leading to a A-type antiferromagnetic coupling of the first TiO2 interface layer with the underlying manganite layer through a superexchange mechanism