Thickness Dependent Topological Hall Effect at SrIrO₃/SrRuO₃ Interface

The Dzyaloshinskii-Moriya interaction (DMI) has recently been found to enable chiral spin structures such as skyrmions, which have potential for next-generation magnetic memory and logic devices. Oxide materials are a desired platform to study novel physics owing to their stability under ambient conditions and tunability through strain. To this end, we study an oxide bilayer system, SrIrO3/SrRuO3, in order to stabilize skyrmions via interfacial DMI. In this system, SrRuO₃ is a ferromagnet while nonmagnetic SrIrO₃ provides strong spin-orbit coupling. We report the synthesis of single crystal SIO/SRO bilayers by off-axis magnetron sputtering, and our epitaxial films were shown to have exceptional crystalline quality by XRD, AFM, and cross section TEM. Our Hall effect measurements reveal a high field topological Hall peak (~1-3 T) below 60 K that cannot be solely accounted for from anomalous Hall signal. In addition, zero field topological Hall signals are consistently seen in a 40 K temperature window below the Curie temperature—independent of thickness. To elucidate these features, we study single layer SRO films which also show zero field topological Hall signals.