A Van der Waals Interface Hosting Two Groups of Magnetic Skyrmions

Abstract

opportunities for exploring magnetism, and toward spintronic applications in the 2D limit. [7][8][9] Among all the interface engineered heterostructures based on vdW layered systems, magnetic proximity effect is integral to manipulating spintronic, [10][11][12] superconducting, [13][14][15] and topological phenomena. [16][17][18] Magnetic skyrmions have been well studied due to their nontrivial topology, which leads to many interesting fundamental and dynamical properties. [19][20][21] These have been reported mostly for noncentrosymmteric single crystals, [22][23][24] ultrathin epitaxial system, [25,26] and magnetic multilayers. [27][28][29][30][31] Recently Néel-type skyrmions were observed in a vdW ferromagnet interfaced with an oxidized layer [32] or a transition metal dichalcogenide [33] with a control of the skyrmion phase through tuning of the ferromagnet thickness. Furthermore, with a variety of vdW magnets, skrymions phase could be created in their new interfaces with unique properties.Materials hosting multiple skyrmion phases add richness to the field, with an additional degree of freedom in designing Multiple magnetic skyrmion phases add an additional degree of freedom for skyrmion-based ultrahigh-density spin memory devices. Extending the field to 2D van der Waals magnets is a rewarding challenge, where the realizable degree of freedoms (e.g., thickness, twist angle, and electrical gating) and high skyrmion density result in intriguing new properties and enhanced functionality. In this work, a van der Waals interface, formed by two 2D ferromagnets Cr 2 Ge 2 Te 6 and Fe 3 GeTe 2 with a Curie temperature of ≈65 and ≈205 K, respectively, hosting two groups of magnetic skyrmions, is reported. Two sets of topological Hall effect signals are observed below 6s0 K when Cr 2 Ge 2 Te 6 is magnetically ordered. These two groups of skyrmions are directly imaged using magnetic force microscopy, and supported by micromagnetic simulations. Interestingly, the magnetic skyrmions persist in the heterostructure with zero applied magnetic field. The results are promising for the realization of skyrmionic devices based on van der Waals heterostructures hosting multiple skyrmion phases.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202110583.

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

“…The corresponding micromagnetic DMI coefficient is about | D | = 0.36 mJ/m 2 . This value is comparable to the other two FGT heterostructures reported recently as promising interfaces to host stable skyrmion states: FGT/In 2 Se 3 (∼0.28 mJ/m 2 ) and FGT/Cr 2 Ge 2 Te 6 (∼0.31 mJ/m 2 ). In the strained heterostructure (γ = −3%) the DMI increases by a factor of about 4 to a value of d ∥ = 1 meV.…”

“…In particular, two independent experimental groups reported the first observation of skyrmions in the van der Waals (vdW) magnets Cr 2 Ge 2 Te 6 and Fe 3 GeTe 2 (FGT) . After that, several experimental groups observed stable skyrmion lattices in 2D magnet vdW heterostructures such as FGT/WTe 2 , FGT/Co/Pd multilayer, and FGT/Cr 2 Ge 2 Te 6 . These exciting measurements have broadened magnetic skyrmion interface platforms from conventional transition-metal films and multilayers to vdW materials consisting of weakly bonded 2D layers.…”

“…20 After that, several experimental groups observed stable skyrmion lattices in 2D magnet vdW heterostructures such as FGT/WTe 2 , 21 FGT/Co/Pd multilayer, 22 and FGT/Cr 2 Ge 2 Te 6 . 23 These exciting measurements have broadened magnetic skyrmion interface platforms from conventional transition-metal films and multilayers to vdW materials consisting of weakly bonded 2D layers. Stabilizing skyrmions in 2D magnets has several potential advantages.…”

Layer-Dependent Magnetic Domains in Atomically Thin Fe5GeTe2

“…Since then, a large and varied assortment of 2D ferromagnets (FMs) and antiferromagnets (AFMs) has been discovered. 4−7 Moreover, exotic magnetic textures, such as skyrmions, have been found in 2D FM-transition metal dichalcogenide (TMDC) 8 and 2D FM-FM 9 heterostructures, as well as oxidized flakes of 2D FMs. 10 In such cases, the antisymmetric exchange interaction, the so-called Dzyalozhinskii−Moriya interaction (DMI), plays a key role in the skyrmion stabilization.…”

Moiré-driven multiferroic order in twisted CrCl$_3$, CrBr$_3$ and CrI$_3$ bilayers

“…We can observe that the ground state spin texture shown in Fig. 2a gets significantly modified due to the strong magnetoelectric coupling, leading to the formation of a magnetic skyrmion around the AA rhombohedral stacking in one of the layers [39,[68][69][70][71][72][73][74]. Interestingly, such a magnetic state features a non-zero total electric polarization in the z-direction.…”