Wafer-scale two-dimensional ferromagnetic Fe3GeTe2 thin films grown by molecular beam epitaxy

Recently, layered two-dimensional ferromagnetic materials (2D FMs) have attracted a great deal of interest for developing low-dimensional magnetic and spintronic devices. Mechanically exfoliated 2D FMs were discovered to possess ferromagnetism down to monolayer. It is therefore of great importance to investigate the distinct magnetic properties at low dimensionality. Here, we report the wafer-scale growth of 2D ferromagnetic thin films of Fe 3 GeTe 2 via molecular beam epitaxy, and their exotic magnetic properties can be manipulated via the Fe composition and the interface coupling with antiferromagnetic MnTe. A 2D layer-by-layer growth mode has been achieved by in situ reflection high-energy electron diffraction oscillations, yielding a well-defined interlayer distance of 0.82 nm along {002} surface. The magnetic easy axis is oriented along c -axis with a Curie temperature of 216.4 K. Remarkably, the Curie temperature can be enhanced when raising the Fe composition. Upon coupling with MnTe, the coercive field dramatically increases 50% from 0.65 to 0.94 Tesla. The large-scale layer-by-layer growth and controllable magnetic properties make Fe 3 GeTe 2 a promising candidate for spintronic applications. It also opens up unprecedented opportunities to explore rich physics when coupled with other 2D superconductors and topological matters. 2D synthesis: molecular beam epitaxy enables growth of ferromagnetic Fe 3 GeTe 2 Molecular beam epitaxy enables wafer-scale growth of Fe 3 GeTe 2 , an atomically thin ferromagnetic compound. A team led by Faxian Xiu at Fudan University demonstrated layer-by-layer growth of large-area, 8 nm-thick films of Fe 3 GeTe 2 on sapphire and GaAs substrates in a high-vacuum molecular beam epitaxy system. The measured Curie temperature of 216.4 K was found to vary systematically with the Fe composition, indicating that Fe doping is a viable route to achieving tailored ferromagnetic ternary compounds with tunable Curie temperature. Furthermore, upon coupling Fe 3 GeTe 2 with antiferromagnetic MnTe, the magnetic properties of the former could be enhanced owing to the exchange interaction from the ferromagnetic/antiferromagnetic superlattice interface. As a result, the coercive field increased by 50% with respect to bare Fe 3 GeTe 2 . These results highlight that Fe 3 GeTe 2 and its heterostructures are promising candidates for spintronic devices.