Coexistence of Merons with Skyrmions in the Centrosymmetric van der Waals Ferromagnet Fe5GeTe2

TL;DR

This study reveals the coexistence of merons and skyrmions in Fe5GeTe2, a centrosymmetric van der Waals ferromagnet, and explores their effects on topological Hall effects and thermal transport, highlighting potential spintronic applications.

Contribution

It demonstrates the coexistence of merons and skyrmions in Fe5GeTe2 and investigates their influence on topological transport properties, including an unconventional Hall effect.

Findings

Coexistence of merons and skyrmions observed via Lorentz TEM.

Detection of topological Hall effect at room temperature.

Unconventional Hall effect attributed to charge-spin interactions.

Abstract

Fe$_{5-x}$GeTe$_2$ is a centrosymmetric, layered van der Waals (vdW) ferromagnet that displays Curie temperatures $T_c$ (270-330 K) that are within the useful range for spintronic applications. However, little is known about the interplay between its topological spin textures (e.g., merons, skyrmions) with technologically relevant transport properties such as the topological Hall effect (THE), or topological thermal transport. Here, we show via high-resolution Lorentz transmission electron microscopy that merons and anti-meron pairs coexist with N\'{e}el skyrmions in Fe$_{5-x}$GeTe$_2$ over a wide range of temperatures and probe their effects on thermal and electrical transport. We detect a THE, even at room $T$, that senses merons at higher $T$s as well as their coexistence with skyrmions as $T$ is lowered indicating an on-demand thermally driven formation of either type of spin texture. Remarkably, we also observe an unconventional THE in absence of Lorentz force and attribute it to the interaction between charge carriers and magnetic field-induced chiral spin textures. Our results expose Fe$_{5-x}$GeTe$_2$ as a promising candidate for the development of applications in skyrmionics/meronics due to the interplay between distinct but coexisting topological magnetic textures and unconventional transport of charge/heat carriers.