Magnetism tunability in wafer-scale few-layered van der Waals ferromagnetic Fe₃GeTe₂films

Two-dimensional (2D) ferromagnetic materials have been discovered with tunable magnetism and nodal-line properties. 2D magnetism modulation in exfoliated nanoflakes via electrostatic gating introduces the boosted T_C. One of the most intriguing challenges, however, is still the realization of high T_C materials that are tunable, robust. Here, we report the effective manipulation of magnetic properties of wafer-scale 2D ferromagnetic Fe₃GeTe₂ films by changing the sample composition and utilizing the proximity effect in ferromagnetic/antiferromagnetic heterostructures. With the film thickness decreasing, T_C drops continuously from 220 K (bulk-like) down to 130 K (few-layer). By varying the sample compositions, T_C will monotonously increase as the ratio changing. T_C behaves a rising trend as the ferromagnetic/antiferromagnetic heterostructure period increases. Our experiments have confirmed the room-temperature T_C and the phase transition, which are consistent with the DFT calculations. The large-scale high-T_C film growth and controllable ferromagnetism of Fe₃GeTe₂ promise the practical spintronic applications. It also opens unprecedented opportunities to explore rich physics in heterostructures of van der Waals ferromagnets with 2D superconductors and topological materials.