the fundamental interest of exploring the spin degree of freedom in unusual electronic environments, but also for exploiting magnetism and spin currents in multifunctional devices. [7,8] Ongoing studies of magnetic 2DEGs focus on novel applications, as well as the search for new magnetic phenomena via, e.g., doping and charge transfer, or imposing epitaxial strain via growth on substrates with different crystal symmetries and lattice parameters. [9][10][11][12][13][14] LaTiO 3 (LTO) and EuTiO 3 (ETO) are two antiferromagnetic (AFM) insulating oxides possessing closely lattice-matched perovskite structures. Along the (001) direction, LTO has formally alternating charged layers (La 3+ O 2-/Ti 3+ O 2-2 ) and ETO has charge-neutral layers (Eu 2+ O 2-/ Ti 4+ O 2-2 ), thus the LTO/ETO interface has

The choice and quality of single-crystal substrates for epitaxial thin film growth drastically influence the properties of the synthesized films. Among them, high-quality substrates with a polar surface are particularly difficult to prepare due to their inherent structural instability against electrostatic forces of the polar discontinuity. As a commonly used insulating substrate, the (111) cut of MgO shows alternating planes of Mg2+ and O2− that form a hexagonal unit cell at the surface, which is useful for thin films with similar crystal symmetries. We present a method to prepare such a surface by first introducing [Formula: see text] reconstructed MgO (111) surface via face-to-face annealing in an O2 environment. We then dissolve the top layers in acid to achieve an unreconstructed and also passivated surface. The structure, stoichiometry, and stability of the resulting surfaces are characterized. This work provides an easy and reliable way to prepare a MgO (111) polar surface ready for subsequent epitaxial growth.