Above Room Temperature Ferromagnetism in All-Epitaxial Fe_5-xGeTe₂/Graphene and Fe_5-xGeTe₂/WSe₂ Van Der Waals Heterostructures

Two-dimensional (2D) magnetic materials are promising building blocks for the realization of novel and ultra-compact devices for spintronics. Moreover, combining them with other 2D crystals to create van der Waals (vdW) heterostructures is a very attractive route to realize hybrid 2D systems exhibiting integrated functionalities. In this contribution, we report recent achievements on scalable epitaxial growth of Fe_5-xGeTe₂ on single crystalline graphene (on SiC) and WSe₂ (on Al₂O₃) templates via molecular beam epitaxy (MBE). Structural studies show that epitaxial Fe_5-xGeTe₂ films with good crystalline quality and sharp vdW interfaces to graphene and WSe₂ could be realized. Importantly, magneto-transport measurements and SQUID magnetometry reveal ferromagnetic order persisting above 350 K with a predominant out-of-plane anisotropy (for the case of Fe_5-xGeTe₂/graphene). These results represent an important advance beyond non-scalable flake exfoliation from bulk crystals, thus marking a crucial step towards the implementation of above room temperature ferromagnetic 2D materials in practical applications.