An X-ray magnetic circular dichroism study of the interface Magnetism in titanate Heterostructures

The 2D-electron system (2DES) created at the interface between LaAlO$_{3}$ and SrTiO$_{3}$ have attracted strong interest in recent years. This system shows an intriguing inversion the Ti3d bands hierarchy at the interface respect the bulk [1], and some reports even suggested coexistence between ferromagnetism and superconductivity [2]. By using x-ray magnetic circular dichroism we show that oxygen vacancies induce magnetic interfacial localized Ti3$+$ states, which couple to the 2DES, with a negative exchange interaction. The magnetic dichroism signal is quenched in standard LAO/STO interfaces annealed in high oxygen pressure after the deposition and showing a homogeneous superconducting ground state [3], suggesting a decisive role of oxygen vacancies in the magnetism of these oxide interfaces [4,5]. \\[4pt] [1] M. Salluzzo, et al. Phys. Rev. Lett. 102, 166804 (2009); M. Salluzzo, et al., Adv. Mater. 25, 2333 (2013).\\[0pt] [2] J.A. Bert, et al., Nature Physics \textbf{7}, 767 (2011).\\[0pt] [3] D. Stornaiuolo, et al., Appl. Phys. Lett. 101, 222601 (2012).\\[0pt] [4] N. Pavlenko, et al., Phys. Rev. B 85, 020407(R) (2012).\\[0pt] [5] M. Salluzzo, et al., Phys. Rev. Lett. 111, 087204 (2013).