  Atomically flat interfaces between ternary oxides have chemically different
variants, depending on the terminating lattice planes of both oxides.
Electronic properties change with the interface termination which affects, for
instance, charge accumulation and magnetic interactions at the interface.
Well-defined terminations have yet rarely been achieved for oxides of ABO3 type
(with metals A, B). Here, we report on a strategy of thin film growth and
interface characterization applied to fabricate the La0.7Sr0.3MnO3-SrRuO3
interface with controlled termination. Ultra-strong antiferromagnetic coupling
between the ferromagnets occurs at the MnO2-SrO interface, but not for the
other termination, in agreement with density functional calculations. X-ray
magnetic circular dichroism measurements reveal coupled reversal of Mn and Ru
magnetic moments at the MnO2-SrO interface. Our results demonstrate termination
control of magnetic coupling across a complex oxide interface and provide a
pathway for theoretical and experimental explorations of novel electronic
interface states with engineered magnetic properties.
