Enhanced spintronic and electronic properties in MTe2-GdCl2 (M=Mo, W) heterojunctions

Two-dimensional ferromagnetic heterojunctions with direct bandgaps and high Curie temperatures (T_C) are promising candidates for applications in nanoelectronics and spintronics. Here, we design a Mo(W)Te₂-GdCl₂ heterojunction by integrating experimentally synthesized monolayer Mo(W)Te₂ with recently predicted ferromagnetic monolayer GdCl₂. Our first-principles calculations reveal that these heterojunctions display a type-II (staggered) band alignment with a narrow direct bandgap ranging from 1.10 to 1.23 eV, using the HSE06 method. We have incorporated spin-orbit coupling and conducted Monte Carlo simulations to precisely estimate the magnetic ground states of these systems. We find that spin-orbit coupling plays a crucial role in the valence band splitting at the K-point in both heterojunctions. The magnetic anisotropy, T_C, and optical performance of individual monolayers are enhanced within these heterojunctions. Under compressive strain, the T_C of the heterojunctions increases significantly, reaching about 278 K at -7 % strain, due to strengthened super-exchange interactions between Gd-d and Cl-p orbitals and enhanced interlayer charge transfer. In addition, the band alignment shifts from type-II to type-I under -3 % compressive strain, while tensile strain maintains the type-II band alignment. Our findings offer a viable pathway for developing ferromagnetic semiconducting heterojunctions suitable for nanoelectronic and spintronic applications.