Giant Topological Hall Effect Across Wide Temperature in Pt/NiCo2O4 Heterostructure

TL;DR

This study reports a giant topological Hall effect in a Pt/NiCo2O4 heterostructure across a wide temperature range, indicating a high density of skyrmion-like spin textures at the interface.

Contribution

It demonstrates the first observation of a giant THE in Pt/NiCo2O4 heterostructures, revealing interfacial topological spin textures and their temperature dependence.

Findings

Giant THE observed from 2 to 350 K.

THE absent in single-layer Pt and NCO, indicating interfacial origin.

High density of skyrmion-like spin textures inferred from normalized THE.

Abstract

Topological Hall effect (THE), a quantum phenomenon arising from emergent magnetic field generated by 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 conducting ferrimagnet NiCo2O4 (NCO) of perpendicular magnetic anisotropy and demonstrate giant THE across a temperature range 2 - 350 K. The absence of THE in 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 nucleation centers. This aligns with the unresolvable domain structures 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.