Boosting the Curie Temperature of Two-Dimensional Semiconducting CrI₃ Monolayer through van der Waals Heterostructures

The integration of ferromagnetic and semiconducting properties in a single two-dimensional (2D) material has been recognized as a fertile ground for fundamental science as well as for practical applications in information processing and storage. CrI3 monolayer has recently drawn much attention due to its 2D long-range ferromagnetic (FM) order. However, its Curie temperature (TC) is too low (∼45 K) for practical spintronic applications. Here, we show that the in-plane FM coupling of CrI3 can be remarkably enhanced by constructing a 2D heterostructure where CrI3 monolayer is supported on a nonmagnetic normal semiconductor/insulator substrate. Choosing MoTe2 monolayer as a substrate, we find that the CrI3/MoTe2 2D heterostructure is an intrinsic semiconducting ferromagnet with TC of ∼60 K. The TC can be further increased to ∼85 K by applying an out-of-plane pressure of ∼4.2 GPa. The doubling of the TC in this 2D heterostructure comes from the introduction of extra spin superexchange (Cr–Te–Cr) paths. Our findings provide a promising pathway to improve ferromagnetism in 2D semiconductors, which can stimulate further theoretical and experimental interest.