Origin of Topological Hall-Like Feature in Epitaxial SrRuO₃ Thin Films

The discovery of topological Hall effect (THE) has important implications for next-generation high-density nonvolatile memories, energy-efficient nanoelectronics, and spintronic devices. Both real-space topological spin configurations and two anomalous Hall effects (AHE) with opposite polarity due to two magnetic phases have been proposed for THE-like feature in SrRuO₃ (SRO) films. In this work, SRO thin films with and without THE-like features are systematically Investigated to decipher the origin of the THE feature. Magnetic measurement reveals the coexistence of two magnetic phases of different coercivity (H_c) in both the films, but the hump feature cannot be explained by the two channel AHE model based on these two magnetic phases. In fact, the AHE is mainly governed by the magnetic phase with higher H_c. A diffusive Berry phase transition model is proposed to explain the THE feature. The coexistence of two Berry phases with opposite signs over a narrow temperature range in the high Hc magnetic phase can explain the THE like feature. Such a coexistence of two Berry phases is due to the strong local structural tilt and microstructure variation in the thinner films. This work provides an insight between structure/micro structure and THE like features in SRO epitaxial thin films.