Large vertical piezoelectricity and high-temperature ferromagnetism in 2D ferromagnetic semiconductors MnAsX (X = I,Br,Cl)

Recently, intrinsic two-dimensional (2D) magnetism has been found to demonstrate good physical and chemical properties, and gradually applied in spintronic devices. Based on first-principles calculations, this letter shows that the monolayers MnAsX (X = Cl, Br, I) are intrinsically ferromagnetic semiconductors. The large piezoelectric coefficients e31 and d31 of the monolayers MnAsX are larger than most TMD family materials because of the broken inversion symmetry along the vertical direction. We also discuss the causes of different bandgaps in MnAsX (X = Cl, Br, I) structure. The mechanism of super-exchange interactions explains the Curie temperature (TC) change from 340 to 542 K as the halogen atoms change from Cl to I. These excellent magnetic properties show the potential of using the 2D family in basic research on spintronic applications.