Thin Films Grown by Molecular Beam Epitaxy

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 FM of Fe₃GeTe₂ via MBE, and their exotic magnetic properties can be manipulated via the film thickness, Fe composition and the interface coupling with antiferromagnetic MnTe. A 2D layer-by-layer growth mode has been achieved by in-situ RHEED 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 (T_C) of 216.4 K. Remarkably, the T_C can be enhanced when reducing the thickness or rising 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 Fe₃GeTe₂ 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.