Angular dependence of Hall effect and magnetoresistance in SrRuO$_3$-SrIrO$_3$ heterostructures.

The perovskite ${\mathrm{SrRuO}}_{3}$ is a prototypical itinerant ferromagnet which allows interface engineering of its electronic and magnetic properties. We report the synthesis and investigation of atomically flat artificial multilayers of ${\mathrm{SrRuO}}_{3}$ with the spin-orbit semimetal ${\mathrm{SrIrO}}_{3}$ in combination with band-structure calculations with a Hubbard $U$ term and topological analysis. The latter reveal an electronic reconstruction and emergence of flat Ru-$4{\mathrm{d}}_{xz}$ bands near the interface, ferromagnetic interlayer coupling, and a negative Berry-curvature contribution to the anomalous Hall effect. We analyze the Hall effect and magnetoresistance measurements as a function of the field angle from an out-of-plane towards an in-plane orientation (either parallel or perpendicular to the current direction) by a two-channel model. The magnetic easy direction is tilted by about ${20}^{\ensuremath{\circ}}$ from the sample normal for low magnetic fields, rotating towards the out-of-plane direction by increasing fields. Fully strained epitaxial growth enables a strong anisotropy of magnetoresistance. An additional Hall effect contribution, not accounted for by the two-channel model, is compatible with stable skyrmions only up to a critical angle of roughly ${45}^{\ensuremath{\circ}}$ from the sample normal. Within about ${20}^{\ensuremath{\circ}}$ from the thin film plane an additional peaklike contribution to the Hall effect suggests the formation of a nontrivial spin structure.