Heterostructures*

O vacancies strongly influence the properties of complex oxides and give rise to novel and unexpected phenomena. Here we combine first-principles density-functional theory with high spatial resolution electron energy-loss spectroscopy and energy-loss magnetic chiral dichroism (EMCD) to show that O vacancies control interface magnetism in La_0.7Sr_0.3MnO₃/SrTiO₃ heterostructures grown by high-pressure O₂ sputtering. EMCD measurements obtained at low temperature (<100K) are sensitive to the local magnetization with atomic resolution, revealing the formation of Ti and the increase of Mn magnetic moments near the interface. Comparison to the calculated electronic properties unambiguously demonstrates the O vacancy origin of the enhanced interface magnetism. The ideal interface - cleavage of bulk components -
shows no charge transfer to the STO, while O vacancies induce finite occupancy of the Ti d-orbitals and hole depletion at the Mn interface planes, enhancing interface magnetism. Our results indicate that the control of O vacancies is a promising approach to improve the magnetic properties of LSMO/STO interfaces.