Influence of the interface atomic structure on the magnetic and electronic properties of La2/3Sr1/3MnO3/SrTiO3(001) heterojunctions

The magnetic and electronic properties of abrupt La2/3Sr1/3MnO3/SrTiO3(001) heterojunctions are investigated by means of generalized gradient approximation (GGA) and GGA+U calculations based on ab initio pseudopotentials. We address, in particular, the influence of the TiO2(001)- and SrO(001) - layer termination of the SrTiO3 at the interface on the magnetic structure, Schottky barrier height, and existence of localized interface states in these junctions. Both interface terminations are found to lead, at zero temperature, to a ferromagnetic coupling between the magnetic moments of the Mn at the junction and in bulk La2/3Sr1/3MnO3. The energy difference, however, between configurations with antiferromagnetic and ferromagnetic alignments at the junction is small in the case of the SrO termination, suggesting that configurations with swapped Mn spins at the interface are likely to occur at ambient temperature. The interface termination has a major influence on the Schottky barrier height. The p-type Schottky barrier height is increased at the abrupt TiO2-terminated interface, relative to the abrupt SrO-terminated junction. Although no minority-spin interface state occurs near the Fermi energy in the abrupt defect-free La2/3Sr1/3MnO3/SrTiO3(001) heterojunctions, low-formation-energy magnetic defects corresponding to swapped Mn spins at the SrO-terminated interface produce localized interface states at the Fermi energy. Such states may jeopardize the spintronic properties of La2/3Sr1/3MnO3/SrTiO3-based structures near room temperature.