Two-dimensional ferromagnetism detected by proximity-coupled quantum Hall effect of graphene

The recent discovery of a two-dimensional van der Waals magnet has paved the way for an enhanced understanding of two-dimensional magnetic systems. The development of appropriate heterostructures in this emerging class of materials is required as the next step towards applications. Here, we report on the electrical transport in monolayer graphene coupled with the two-dimensional ferromagnet Cr₂Ge₂Te₆ (CGT). Graphene that forms an interface with CGT is electron-doped owing to charge transfer. The temperature-dependent resistance of graphene/CGT undergoes a nontrivial sudden change near the Curie temperature (T_c) of CGT. Apart from this, the behavior of various transport parameters also differs before and after T_c. Moreover, the contribution of the magnetization of CGT to the enhanced magnetic flux density leads to the critical evolution of the quantum Hall state. These results imply that graphene in the graphene/CGT hybrid structure can be utilized to electrically monitor the magnetic phase transition of the adjacent CGT layer.