The heterostructures of the ferromagnet (Cr2Te3) and topological insulator (Bi2Te3) have been grown by molecular beam epitaxy. The topological Hall effect as evidence of the existence of magnetic skyrmions has been observed in the samples in which Cr2Te3 was grown on top of Bi2Te3. Detailed structural characterizations have unambiguously revealed the presence of intercalated Bi bilayer nanosheets right at the interface of those samples. The atomistic spin-dynamics simulations have further confirmed the existence of magnetic skyrmions in such systems. The heterostructures of ferromagnet and topological insulator that host magnetic skyrmions may provide an important building block for next generation of spintronics devices.

Materials with perpendicular magnetic anisotropy (PMA) effect with high Curie temperature is essential in applications. Cr2Te3 is a material that demonstrates PMA effect but with a relatively low Curie temperature of about 180 K. In this work, Cr 2 Te 3 thin films with Curie temperature ranging from 165 K to 295 K were successfully grown on Al2O3 by the molecular beam epitaxy (MBE) technique. To study the physical origin of the improved Curie temperature, structural analysis, magneto-transport and magnetic characterizations were conducted and analyzed in detail. In particular, the n-type feature of these thin films shows that they are an electron-enriched material. Ferromagnetic (FM) ordering and Anti Ferromagnetic (AFM) ordering competition were systematically investigated by magnetization characterizations. A 2 phenomenological model based on the degree of coupling between FM and AFM ordering was proposed to explain the observed Currie temperature enhancement in our samples. These findings indicate that the Curie temperature of Cr 2 Te 3 thin films can be tuned and our material could act as a novel magnetic material with potential for various magnetic applications.

We implement the molecular beam epitaxy method to embed the black-phosphorus-like bismuth nanosheets into the bulk ferromagnet Cr2Te3. As a typical surfactant, bismuth lowers the surface tensions and mediates the layer-by-layer growth of Cr2Te3. Meanwhile, the bismuth atoms precipitate into black-phosphorus-like nanosheets with the lateral size of several tens of nanometers. In Cr2Te3 embedded with Bi-nanosheets, we observe simultaneously a large topological Hall effect together with the magnetic susceptibility plateau and magnetoresistivity anomaly. As a control experiment, none of these signals is observed in the pristine Cr2Te3 samples. Therefore, the Bi-nanosheets serve as seeds of topological Hall effect induced by non-coplanar magnetic textures planted into Cr2Te3. Our experiments demonstrate a new method to generates a large topological Hall effect by planting strong spin-orbit couplings into the traditional ferromagnet, which may have potential applications in spintronics.