The magnetic and electronic nature of the γ-Al2O3/SrTiO3 spinel/perovskite interface is explored by means of x-ray absorption spectroscopy. Polarized x-ray techniques combined with atomic multiplet calculations reveal localized magnetic moments assigned to Ti3+ at the interface with equivalent size for in- and out-of-plane magnetic field directions. Although magnetic fingerprints are revealed, the Ti3+ magnetism can be explained by a paramagnetic response at low temperature under applied magnetic fields. Modeling the x-ray linear dichroism results in a Δ0 ∼ to 1.9 eV splitting between the t(2g) and e(g) states for the Ti4+ 3d(0) orbitals. In addition these results indicate that the lowest energy states have the out-of-plane d(xz)/d(yz) symmetry. The isotropic magnetic moment behavior and the lowest energy states d(xz)/d(yz) are in contrast to the observations for the two-dimensional electron gas at the perovskite/perovskite interface of LaAlO3/SrTiO3 that exhibits an anisotropic magnetic d(xy) ground state.
Mardegan, J. R. L., Christensen, D. V., Chen, Y. Z., Parchenko, S., Avula, S. R., Ortiz-Hernandez, N., Decker, M., Piamonteze, C., Pryds, N., & Staub, U. (2019). Magnetic and electronic properties at the γ-Al2O3/SrTiO3 interface. Physical Review B, 99(13), . https://doi.org/10.1103/PhysRevB.99.134423