Prediction of antiferromagnetic metal-rich chalcogenide monolayers M2X (M = Ti, Zr, Hf and X = S, Se, Te) with high Neel temperature

We predict by first-principles calculations a new kind of binary metal-rich chalcogenide monolayers M2X (M = Ti, Zr, Hf and X = S, Se, Te), anti-structure of transition metal dichalcogenides, and study their stability, electronic structures and magnetic properties. This system is an intrinsic two-dimensional antiferromagnetic semiconductor. The magnetic ground state can be expressed as ferromagnetic ordering in a M atomic layer with antiferromagnetic coupling between two M atomic layers. The intralayer ferromagnetic ordering originates from the intralayer ferromagnetic d-p(x) / p(y)-d super-exchange interaction and the interlayer antiferromagnetism comes from the interlayer d-p(z)-d antiferromagnetic coupling through chalcogenide elements. The monolayers have large perpendicular magnetic anisotropic energy and can be up to 2000 mu eV/cell for Hf2X. The anisotropy energy decreases by one order of magnitude when the metal atom M changes from Hf to Ti. In addition, the calculated Neel temperature can reach or even exceed the room temperature. Our findings suggest that the M2X may have potential application in the fields of spintronics, and will promote further theoretical and experimental study of the compounds with the anti-structure of transition metal dichalcogenides.