Electronic and magnetic properties of single-layer and double-layer VX 2 (X = Cl, Br) under biaxial stress* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11904312 and 11904313), the Project of Hebei Educational Department, China (Grant Nos. ZD2018015 and QN2018012), and the Natural Science Foundation of Hebei Province, China (Grant No. A2019203507).

Abstract

First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX 2 (X = Cl, Br) can be tuned from antiferromagnetic (AFM) semiconductors to ferromagnetic (FM) state when biaxial tensile stress is applied. Their ground states are all T phase. The biaxial tensile stress at the phase transition point of the double-layer VX 2 is larger than that of the single-layer VX 2. The direct band gaps can be also manipulated by biaxial tensile stress as they increases with increasing tensile stress to a critical point and then decreases. The Néel temperature (T N) of double-layer VX 2 are higher than that of single-layer. As the stress increases, the T N of all materials tend to increase. The magnetic moment increases with the increase of biaxial tensile stress, and which become insensitive to stress after the phase transition points. Our research provides a method to control the electronic and magnetic properties of VX 2 by stress, and the single-layer and double-layer VX 2 may have potential applications in nano spintronic devices.