Visualizing the Effect of Oxidation on Magnetic Domain Behavior of Nanoscale Fe3GeTe2 for Applications in Spintronics

Magnetic van der Waals (vdW) materials offer an opportunity to design heterostructures that wi l l lead to exotic functionalities that arise from interfacial interaction. In addition to coupling to different v d W materials, the naturally oxidized surface layer of a v d W material also forms a heterostructure with its bul k film, giving rise to intriguing phenomena. Here, we directly observe the impact of oxidation on the magnetic domains, namely, magnetic stripe domain and skyrmions, in a nanoscale Fe3GeTe2 flake using cryo Lorentz transmission electron microscopy. After the Fe3GeTe2 is exposed to ambient conditions, partial oxidation leads to an increase in the density of skyrmions even under zero magnetic field . Complete oxidation leads to a loss of the magnetic domain structure. We observe a gradual change in Fe3GeTe2 from single crystal to amorphous as the oxidation increases. The oxidized Fe3GeTe2 primarily consists of iron oxide, which could be antiferromagnetic in nature. We hypothesize that the interfacial interaction between these surface antiferromagnetic oxides and the bu l k ferromagnetic Fe3GeTe2, as wel l as the effect of interfacial roughness, leads to the increase in Neel skyrmion creation. This work opens a path to harness controlled oxidation as a build block to create dense skyrmion lattices without the need for an external magnetic field, leading to potential future applications in spintronic devices.