Observation of Magnetic Skyrmion Bubbles in a van der Waals Ferromagnet Fe3GeTe2

Abstract

Two-dimensional (2D) van der Waals (vdW) materials are a family of quantum materials that have attracted great research attention in the past decade as they possess a diverse range of novel phenomena which are promising for technological applications. Among these materials, Fe3GeTe2 (FGT) is only ferromagnetic metal, exhibiting a strong out-of-plane uniaxial magnetic anisotropy down to atomic-layer thicknesses, [1-4] which is very critical for spintronic applications, typically, magnetic-tunneling-junctions and magnetic random-access-memory devices. In this talk, we will show that a Bloch-type magnetic skyrmion bubble can indeed be realized in the single crystals of 2D vdW FGT. A high-density hexagonally-packed lattice of skyrmion bubbles emerges by a simple field-cooling process and keeps stable after turning off the magnetic field.[5] Besides, we will show that the density of field free skyrmion lattice was tuned by changing the value of the cooling magnetic field. The highest-density skyrmion bubble was obtained when the field was applied at H = 500 Oe. As the value of the magnetic field is increasing, the size of the skyrmion is increasing but the density of skyrmion is decreasing. When the field is higher than 800 Oe, only stripe domain is observed. Finally, we will show the results from the miromagnetic simulations. We found that total energy of the skyrmion lattice is higher than than energy of the stripe domain, which indicates that the field free skyrmions is metastable state compared with ferromagnetic state. We believe the results presented in this talk could be useful for understanding the topological spin textures physics in 2D vdW materials. **