Giant topological Hall effect in epitaxial Ni$_{80}$Fe$_{20}$/La$_{0.65}$Sr$_{0.35}$MnO$_3$ thin film heterostructures

TL;DR

This study reports a giant topological Hall effect at room temperature in epitaxial NiFe/LaSrMnO3 heterostructures, attributed to interfacial Rashba interaction and skyrmion-like features, with implications for spintronics.

Contribution

It demonstrates a large topological Hall effect in Py/LSMO heterostructures driven by interfacial Rashba interaction and skyrmion formation, a novel finding in oxide heterostructures.

Findings

Giant topological Hall resistivity of ~2.8 μΩ·cm observed at room temperature.

Enhanced topological Hall effect with ferroelectric BaTiO3 layer.

Skyrmion-like features detected via magnetic force microscopy.

Abstract

The emergence of new physical properties at the interfaces between complex oxides has always been of both fundamental and practical importance. Here, we report the observation of a giant topological Hall resistivity of $\sim 2.8 \mu \Omega$ \text{cm} at room temperature in an epitaxial thin-film heterostructure of permalloy (Py, Ni$_{80}$Fe$_{20}$) and the half-metallic ferromagnet La$_{0.65}$Sr$_{0.35}$MnO$_3$ (LSMO). This large magnitude of the topological Hall effect in the Py/LSMO heterostructure, compared to a single-layer Py thin film, is attributed to the optimized combination of ferromagnetism in LSMO and the strong spin-orbit-coupling-driven Rashba interaction at the interface. The introduction of a ferroelectric BaTiO$_3$ (BTO) sandwich layer in the Py/LSMO heterostructure also leads to an enhanced topological Hall resistivity compared to the single-layer Py thin film. Interestingly, magnetic force microscopy measurements reveal skyrmion-like features, suggesting the origin of the topological Hall effect. Our theoretical model calculations for the skyrmion lattice further indicate that the Rashba interaction, driven by the broken inversion symmetry in the Py/LSMO films, can account for the observed changes in the topological Hall effect at the interface. Our work opens the door for the potential use of Py/LSMO thin films in spintronic applications.