Topological Signatures in the Hall Effect of SrRuO3/La0.7Sr0.3MnO3 SLs

Noncollinear spin textures such as skyrmions lead to a novel Hall effect contribution called the topological Hall effect. In recent years, research has focused on the Weyl metal SrRuO3 with topological signatures reported for SrRuO3 layers adjacent to layers with strong spin-orbit coupling. However, SrRuO3 films are known to be prone to structural modifications when interfaced with different materials. In this work the Hall effect of SrRuO3/La0.7Sr0.3MnO3 superlattices (SLs) is correlated with structural and magnetic information to study whether a topological Hall effect is induced by interfacing to ferromagnetic layers. High-quality SLs with ultrathin layers are fabricated by pulsed laser deposition on SrTiO3 substrates. The symmetry of the SrRuO3 layers is studied by angular magnetoresistance measurements and the magnetocrystalline anisotropy by magnetization measurements. Two SLs are compared in detail, both with 8 unit cell thick SrRuO3 layers, but with La0.7Sr0.3MnO3 layers 2 and 4 unit cell thick. Only the sample with 2 unit cell thick manganite layers shows features resembling a topological Hall effect. Depending on the La0.7Sr0.3MnO3 layer thickness the SrRuO3 crystalline symmetry is orthorhombic or tetragonal. The results indicate that the topological Hall effect features arise from an intricate interplay between magnetocrystalline anisotropy and antiferromagnetic interlayer coupling.