Chiral Spin Spirals at the Surface of the van der Waals Ferromagnet Fe$_3$GeTe$_2$

TL;DR

This study reveals chiral Neel spin spirals on the surface of Fee3GeTe2, a van der Waals ferromagnet, persisting up to its Curie temperature, indicating potential for chiral magnetism in layered materials.

Contribution

First observation of chiral Neel spin spirals on Fee3GeTe2 surface, suggesting positive Dzyaloshinskii-Moriya interaction in this van der Waals ferromagnet.

Findings

Chiral Neel spin spirals observed at zero magnetic field.

Spin spirals persist up to Curie temperature with stable periodicity.

Evidence of positive Dzyaloshinskii-Moriya interaction in Fee3GeTe2.

Abstract

Topologically protected magnetic structures provide a robust platform for low power consumption devices for computation and data storage. Examples of these structures are skyrmions, chiral domain walls, and spin spirals. Here we use scanning electron microscopy with polarization analysis to unveil the presence of chiral counterclockwise N\'eel spin spirals at the surface of a bulk van der Waals ferromagnet Fe$_3$GeTe$_2$ (FGT), at zero magnetic field. These N\'eel spin spirals survive up to FGT's Curie temperature $T_\mathrm{C}= 220 \mathrm{~K}$, with little change in the periodicity $p=300 \mathrm{~nm}$ of the spin spiral throughout the studied temperature range. The formation of a spin spiral showing counterclockwise rotation strongly suggests the presence of a positive Dzyaloshinskii-Moriya interaction in FGT, which provides the first steps towards the understanding of the magnetic structure of FGT. Our results additionally pave the way for chiral magnetism in van der Waals materials and their heterostructures.