Conformal Growth of Cr2Te3 on Bi2Te3 Nanodots with a Topological Hall Effect

The conformal growth of a high-quality ferromagnet (Cr2Te3) on the nanostructures of a topological insulator (Bi2Te3) was realized via molecular beam epitaxy (MBE). A large topological Hall effect (THE) (similar to 400 n Omega cm) was unambiguously observed up to 95 K, which provided the evidence for the existence of magnetic spin textures such as magnetic skyrmions in this system. Detailed atomic structure characterizations revealed that black-phosphorus-like Bi nanosheets were embedded in the Cr2Te3 lattice and densely stacked above the Bi2Te3 nanodots. A nanoscale formation mechanism of the embedded Bi nanosheets was then proposed, demonstrating that the embedded Bi nanosheets were released from the Bi2Te3 nanodots in the van der Waals epitaxy process of Cr2Te3. Remarkably, as the large spin-orbital coupling of the embedded Bi nanosheets can stimulate the generation of magnetic skyrmions at the interfaces between them and Cr2Te3, the observed large THE may be attributed to the skyrmions on the densely stacked Bi nanosheets. In summary, our findings demonstrate the reaction between transition-metal Cr and Bi2Te3 in the conformal growth of Cr2Te3 on Bi2Te3 nanodots and provide an efficient and scalable technique to realize future spintronic devices.