Probing Skyrmion Phases in SrIrO₃/SrRuO₃ thin film by Topological Hall Minor Loops

Skyrmions are topological quasi-particles promising for next generation magnetic storage devices. Fundamental understanding of how field history affects skyrmion formation in host materials is vital in regards to technological application. Topological Hall effect is one of major techniques in probing the skyrmion formation. Magnetization and Hall minor hysteresis loops could reveal critical information in addition to traditional full loops. Here we show Hall minor loops of a SrIrO₃/SrRuO₃ bilayer, which host nanoscale skyrmions as revealed by pronounced topological Hall effect. At low temperature Hall minor loops track the magnetization reversal process, indicating that the skyrmion formation is closely related to magnetization reversal. However, at high temperatures, the Hall resistivity switches before reaching zero field induced by the dominant topological Hall effect; furthermore, the Hall minor loops reveal truly novel behavior that significantly deviates from the magnetization minor loops. We propose such behaviors could due to stabilization of skyrmions even when applied field is larger than magnetization coercive field.