Topological Magneto-optical Effect from Skyrmions in Two-Dimensional Ferromagnets.

Skyrmions in two-dimensional (2D) magnetic materials are considered as ideal candidates for information carriers in next-generation spintronic devices. However, conventional methods for elucidating the physical properties of skyrmions have limited the development of skyrmions in diverse 2D magnetic material systems due to their requirements for electrical conductivity. To overcome this limitation, we propose to utilize an optical method (magneto-optical Kerr technique) to detect the skyrmions in 2D magnetic materials. Herein, the graphene/FeGeTe/graphene vertical van der Waals (vdW) heterostructure devices are fabricated to generate stabilized skyrmions by applying out-of-plane current. In combination with magnetic circular dichroism measurements, we observe topological-reflective magnetic circular dichroism (T-RMCD) effects in FeGeTe flakes and attribute the peak-shaped component in T-RMCD to the annihilation of skyrmion magnetic domains. Notably, the T-RMCD signal can maintain up to a temperature as high as the Curie temperature of FeGeTe flakes (∼200 K). Our work provides a universal, contactless, and nondestructive approach for studying the physical properties of skyrmions in 2D vdW magnetic materials while adding another degree of freedom to the modulation of skyrmions.