High-temperature ferromagnetic semiconductors: Janus monolayer vanadium trihalides

Two-dimensional intrinsic ferromagnetic semiconductors are expected to stand out in the spintronic field. Recently, monolayer VI3 was experimentally synthesized, but the weak ferromagnetism and low Curie temperature T-C limit its potential application. Here we report that the Janus structure can elevate TC to 240 K. And we discuss the reason for high T-C in the Janus structure, which is the lower virtual exchange gap between t(2g) and e(g) states of nearest-neighbor V atoms. In addition, T-C can be further substantially enhanced by tensile strain due to the increasing ferromagnetism driven by rapidly quenched direct exchange interaction. Our work supports a feasible approach to enhance Curie temperature of monolayer VI3 and unveils stable intrinsic FM semiconductors for realistic applications in spintronics.