Giant topological Hall effect across a wide temperature range in Pt/NiCo2O4 heterostructures

Abstract

The topological Hall effect (THE), a quantum phenomenon arising from the emergent magnetic field generated by a topological spin texture, is a key method for detecting non-coplanar spin structures like skyrmions in magnetic materials. Here, we investigate a bilayer structure of Pt and the conducting ferrimagnet NiCo2O4 (NCO) of perpendicular magnetic anisotropy and demonstrate a giant THE across a temperature range of 2–350 K. The absence of THE in a single-layer Pt and NCO, as well as in Pt/Cu/NCO, suggests its interfacial origin. The maximum THE occurring just before the NCO coercive field indicates its connection to magnetic nucleation centers, which are topologically equivalent to skyrmions. The large normalized THE, based on the emergent-field model, points to a high population density of small magnetic nucleation centers. This aligns with the seemingly unresolvable domain structures by the employed techniques during magnetization reversal, even though clear domain structures are detected after zero-field cooling. These results establish heavy metal/NCO as a promising system for exploring topological spin structures.