title: Competition between covalent bonding and charge transfer at complex-oxide interfaces.
abstract: Here we study the electronic properties of cuprate-manganite interfaces. By means of atomic resolution electron microscopy and spectroscopy, we produce a subnanometer scale map of the transition metal oxidation state profile across the interface between the high Tc superconductor YBa2Cu3O7-δ and the colossal magnetoresistance compound (La,Ca)MnO3. A net transfer of electrons from manganite to cuprate with a peculiar nonmonotonic charge profile is observed. Model calculations rationalize the profile in terms of the competition between standard charge transfer tendencies (due to band mismatch), strong chemical bonding effects across the interface, and Cu substitution into the Mn lattice, with different characteristic length scales.
authors.affiliation: Grupo de Física de Materiales Complejos, Universidad Complutense, 28040 Madrid, Spain and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Salafranca
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Julián
authors.initials: J
authors.lastname: Rincón
authors.affiliation: Grupo de Física de Materiales Complejos, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Tornos
authors.affiliation: Grupo de Física de Materiales Complejos, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: León
authors.affiliation: Grupo de Física de Materiales Complejos, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Jacobo
authors.initials: J
authors.lastname: Santamaria
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Elbio
authors.initials: E
authors.lastname: Dagotto
authors.affiliation: Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Pennycook
authors.affiliation: Grupo de Física de Materiales Complejos, Universidad Complutense, 28040 Madrid, Spain and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Varela