[en] The electronic structure of SrTiO3 and SrHfO3 (001) surfaces with oxygen vacancies is studied by means of
first-principles calculations. We reveal how oxygen vacancies within the first atomic layer of the SrTiO3 surface
(i) induce a large antiferrodistortive motion of the oxygen octahedra at the surface, (ii) drive localized magnetic
moments on the Ti 3d orbitals close to the vacancies, and (iii) form a two-dimensional electron gas localized
within the first layers. The analysis of the spin texture of this system exhibits a splitting of the energy bands
according to the Zeeman interaction, lowering of the Ti 3dxy level in comparison with dxz and dyz, and also
an in-plane precession of the spins. No Rashba-like splitting for the ground state or for the ab initio molecular
dynamics trajectory at 400 K is recognized as suggested recently by A. F. Santander-Syro et al. [Nat. Mater. 13,
1085 (2014)]. Instead, a sizable Rashba-like splitting is observed when the Ti atom is replaced by a heavier Hf
atom with a much larger spin-orbit interaction. However, we observe the disappearance of the magnetism and the surface two-dimensional electron gas when full structural optimization of the SrHfO3 surface is performed. Our results uncover the sensitive interplay of spin-orbit coupling, atomic relaxations, and magnetism when tuning these Sr-based perovskites.
Kuschel, T., Reiss, G., (2014) Nat. Nanotechnol., 10, p. 22
Zhang, W., Jungfleisch, M.B., Jiang, W., Sklenar, J., Fradin, F.Y., Pearson, J.E., Ketterson, J.B., Hoffmann, A., (2015) J. Appl. Phys., 117, p. 172610