The magnetic and electronic nature of the $\gamma \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3/{\mathrm{SrTiO}}_3$ 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 ${\mathrm{Ti}}^{3+}$ at the interface with equivalent size for in- and out-of-plane magnetic field directions. Although magnetic fingerprints are revealed, the ${\mathrm{Ti}}^{3+}$ magnetism can be explained by a paramagnetic response at low temperature under applied magnetic fields. Modeling the x-ray linear dichroism results in a ${\mathrm{\Delta }}_0\sim 1.9$ eV splitting between the $t_{2g}$ and $e_g$ states for the ${\mathrm{Ti}}^{4+}3d^0$ 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 $d_{xz}/d_{yz}$ states are in contrast to the observations for the two-dimensional electron gas at the perovskite/perovskite interface of ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ that exhibits an anisotropic magnetic $d_{xy}$ ground state.

• Received 28 January 2019

DOI:https://doi.org/10.1103/PhysRevB.99.134423