Above Room-Temperature Ferromagnetism in Wafer-Scale Two-Dimensional van der Waals Fe₃GeTe₂ Tailored by a Topological Insulator

Abstract

The emerging two-dimensional ferromagnetic materials present atomic layer thickness and a perfect interface feature, which have become an attractive research direction in the field of spintronics for low power and deep nanoscale integration. However, it has been proven to be extremely challenging to achieve a room-temperature ferromagnetic candidate with well controlled dimensionality, large-scale production, and convenient heterogeneous integration. Here, we report the growth of wafer-scale two-dimensional Fe3GeTe2 integrated with a topological insulator of Bi2Te3 by molecular beam epitaxy, which shows a Curie temperature (T c ) up to 400 K with perpendicular magnetic anisotropy. Dimensionality-dependent magnetic and magnetotransport measurements find that T c increases with decreasing Fe3GeTe2 thickness in the heterostructures, indicating an interfacial engineering effect from Bi2Te3. The theoretical calculation further proves that the interfacial exchange coupling could significantly enhance the intralayer spin interaction in Fe3GeTe2, hence giving rise to a higher T c . Our results provide great potential for the implementation of high-performance spintronic devices based on two-dimensional ferromagnetic materials.

Recent Progress in Proximity Coupling of Magnetism to Topological Insulators

“…Researchers have already started exploiting this strategy to engineer higher T c in magnetic materials. [ 106,107 ] A complete understanding of these type of mechanisms is necessary for successful manipulation of magnetic proximity effect in TI.…”

“…Indeed there is tantalizing experimental evidence of significantly elevated T c in both the interfacial magnetism in the TI and the MM layer, even surpassing room temperature. [ 104–107 ]…”

Recent Advances in Two-Dimensional Spintronics

“…For example, based on the mechanism of spin relaxation, theory predicted that the spin lifetime for pristine graphene would be up to 1 μs, whereas experimental values range from tens of picoseconds to a few nanoseconds [14,57,103]. Furthermore, the spin injection efficiency of graphene measured experimentally ranges from a few percent to 10%, which is far smaller than the theoretical prediction value of 60-80% [125]. These differences indicate that more in-depth physical mechanisms and accurate theoretical models need to be proposed and developed to better guide the research direction and analyze the experimental results.…”

Spin‐Orbit Torque in Van der Waals‐Layered Materials and Heterostructures

“…Assembling the vdW heterostructure with other materials may also be helpful in enhancing the T C of vdW magnets. [163,171,172] In addition, doping, such as, Ga implantion and Co doping were recently demonstrated to be effective to increase the T C . [173][174][175] Finally, wafer-scale scalability of vdW materials is still an important issue.…”