Emergent Topological Hall Effect from Exchange Coupling in Ferromagnetic Cr₂Te₃/Noncoplanar Antiferromagnetic Cr₂Se₃ Bilayers

Abstract

The topological Hall effect has been observed in magnetic materials of complex spin structures or bilayers of trivial magnets and strong spin–orbit-coupled systems. In view of current attention on dissipationless topological electronics, the occurrence of the topological Hall effect in new systems or by an unexpected mechanism is fascinating. Here, we report a robust topological Hall effect generated in bilayers of a ferromagnet and a noncoplanar antiferromagnet, from the interfacial Dzyaloshinskii–Moriya interaction due to the exchange coupling of magnetic layers. Molecular beam epitaxy has been utilized to fabricate heterostructures of a ferromagnetic metal Cr2Te3 and a noncoplanar antiferromagnet Cr2Se3. A significant topological Hall effect at low temperature implies the development of nontrivial spin chirality, and density functional theory calculations explain the correlation of the Dzyaloshinskii–Moriya interaction increase and inversion symmetry breaking at the interface. The presence of noncoplanar ordering in the antiferromagnet plays a pivotal role in producing the topological Hall effect. Our results suggest that the exchange coupling in ferromagnet/noncoplanar antiferromagnet bilayers could be an alternative mechanism toward topologically protected magnetic structures.

Strain-tunable Berry curvature in quasi-two-dimensional chromium telluride

“…These hump-shaped Hall peaks in our pristine Cr 2 Te 3 are related to the presence of strain-modulated magnetic multilayer/domain structures with opposite signs of AHE (Fig. 5a ), and not to the skyrmion-induced topological Hall effect as postulated in various heterostructures 38 – 40 , 42 – 44 , 48 .

Fig.

…”

Giant 2D Skyrmion Topological Hall Effect with Ultrawide Temperature Window and Low-Current Manipulation in 2D Room-Temperature Ferromagnetic Crystals

“…2(d Before discussing the 2D THE in sub-20 nm O-FGaT/FGaT, it is necessary to review some recent criticisms about the artifact "THE". [24] Based on recently reported distinguishing methods, [25,26] the possibility of the artifact THE has been discussed and eliminated (see more discussions in Note S3 and Fig. S9 of the Supplemental Material), thereby implying that the observed 2D THE may originate from topologically nontrivial spin textures such as magnetic skyrmions.…”

Epitaxial van der Waals heterostructures of Cr2Te3 on two-dimensional materials

“…Highly efficient control of magnetic properties is required for spintronic applications [5], and it is, therefore, necessary to understand the growth mechanisms of these materials, especially for the development of functional vdW heterostructures. Exotic topological phenomena such as the topological Hall effect have also been reported in Cr 2 Te 3 /Bi 2 Te 3 bilayers [20,21] and Cr 2 Te 3 /Cr 2 Se 3 [22]. Moreover, noncollinear spin textures were shown in Cr 2 Te 3 as a consequence of antiferromagnetic coupling between neighboring chromium atoms [23], making it an interesting host for exotic, trivial, or topological spin textures.…”

“…For this purpose, 2D ferromagnets with Curie temperatures T C higher than room temperature and with perpendicular magnetic anisotropy (PMA) are required [7]. Fe x GeTe 2 (x = 3, 4, or 5) [8] and Cr 1+δ Te 2 (0 δ 1) [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] emerged recently as the two most promising families of materials to * These authors contributed equally to this work. achieve such conditions.…”