Strain-Driven Zero-Field Near-10 nm Skyrmions in Two-Dimensional van der Waals Heterostructures

Abstract

Magnetic skyrmionslocalized chiral spin structuresshow great promise for spintronic applications. The recent discovery of two-dimensional (2D) magnets opened new opportunities for topological spin structures in atomically thin van der Waals (vdW) materials. Despite recent progress in stabilizing metastable skyrmions in 2D magnets, their lifetime, essential for applications, has not been explored yet. Here, using first-principles calculations and atomistic spin simulations, we predict that compressive strain leads to stabilizing zero-field skyrmions with diameters close to 10 nm in a Fe3GeTe2/germanene vdW heterostructure. The origin of these unique skyrmions is attributed to the high tunability of Dzyaloshinskii–Moriya interaction and magnetocrystalline anisotropy energy by strain, which generally holds for Fe3GeTe2 heterostructures with buckled substrates. Furthermore, we calculate the energy barriers protecting skyrmions against annihilation and their lifetimes using transition-state theory. We show that nanoscale skyrmions in strained Fe3GeTe2/germanene can be stable for hours at temperatures up to 20 K.

Tuning the magnetic interactions in van der Waals Fe3GeTe2 heterostructures: A comparative study of ab initio methods

“…The extracted |D| is about 1.5 mJ/m 2 at γ = −3%, which is comparable to the value previously estimated in FM/HM thin-film systems [12,18,47,49]. Such a large DMI indicates that the FGT/Ge heterostructure can be a promising interface for stable isolated skyrmions [58]. A more detailed analysis shows that the enhancement of the DMI in FGT/Ge is mainly mediated by the geometrical change due to the buckled structure of germanene (see Sec.…”

“…However, the MAE is dramatically reduced to 25% of its original value at a compressive strain of γ = −3%. In connection with the exchange frustration in FGT/germanene, these large changes in the DMI and MAE open the possibility of zero-field magnetic skyrmions [58]. For the DMI in FGT/Ge, the three theoretical approaches are in good qualitative agreement, and we also discuss the quantitative comparison in detail.…”

“…The motivation behind the use of germanene as a nonmagnetic layer is as follows. We recently demonstrated that the buckled structure of germanene could enhance the structural asymmetry of FGT under strain [58]. More importantly, such an efficient strain-driven DMI control is general for FGT heterostructures with buckled substrates (e.g., silicene and antimonene).…”

Monolayers of Germanene/Janus Ga2SeTe van der Waals Heterostructures by First-Principles Calculations for High-Performance Optoelectronic Devices

“…van der Waals heterostructures (vdWHs), which are vertically stacked by two 2D materials, have been considered to be promising candidates for optoelectronic devices, photocatalysis, − and spintronics. − Inspired by the traditional 2D vdWHs, researchers have theoretically proposed various heterostructures based on Janus 2D materials to explore their novel properties. In recent years, Janus vdWHs have been widely studied and classified into three categories: Janus TMDs–TMDs, , Janus TMDs–graphene, , and heterostructures composed of Janus TMDs and other traditional 2D materials. − Many studies have found that these Janus vdWHs exhibited promising potential in terms of electronic properties, photocatalytic properties, Rashba effect, and piezoelectric effect.…”

Laser-induced topological spin switching in a 2D van der Waals magnet

“…Different spin textures have been previously observed in vdW magnets (e.g., Fe 3 GeTe 2 , CrCl 3 , Cr 2 Te 3 , Fe 5 GeTe 2 , CrGeTe 3 ). They range from magnetic bubbles 11,31,32 and stripe domains 33 , up to topological quasiparticles, such as skyrmions [34][35][36][37][38][39][40] and merons 2,41 , as recently summarised in the 2D Magnetic Genome 1 . These evidences provide a broad territory for exploration either in more fundamental levels or in functional applications where the control of spin textures in device platforms is the ultimate step.…”