Topological Hall Effect in Ultra-thin SrRuO₃ film

With extensive interests on novel oxide-based devices such as electronics and spintronics, the 4d transition metal compounds have been considered as promising candidates. Especially, SrRuO₃ is well-known for an itinerant ferromagnetic metal with a high Curie temperature , leading to anomalous Hall effect (AHE) below . Owing to the intense study on Hall effect in SrRuO₃ thin films, the mechanism of Hall effect has been well-established. Here, we observed extraordinary Hall effect in high-quality SrRuO₃ ultra-thin films grown by pulsed laser deposition (PLD), which cannot be explained in terms of simple AHE. We claim that this extraordinary Hall effect can be understood as topological Hall effect, which occurs due to emergent electromagnetic field (EEMF) derived from Skyrmion spin texture. Moreover, the Skyrmion phase is extremely stable with sustaining large external magnetic field range, about 1 Tesla. We suggest that the large spin orbit coupling of Ru ions and the inversion symmetry breaking produce Dzyaloshinskii-Moriya (DM) interaction and consequently the Skyrmion phase is formed in ultra-thin SrRuO₃ film.