Prediction of novel 2D metallic ferroelastic ferromagnet: Monoclinic CrTe2

By combining the USPEX evolutionary algorithm and density functional theory at the HSE06 level, we identified a new CrTe2 monolayer crystallizing in monoclinic phase with C2h symmetry, which is different from the well-known 1T-CrTe2 monolayer. The monoclinic phase is energetically favored over that in 1T phase, is thermo-dynamically, dynamically, and mechanically stable. The monoclinic phase is an intrinsically ferromagnetic metal with a relatively high Curie temperature of 215 K showing an out-of-plane easy axis with 25 degrees off the z-axis. In particular, the predicted Curie temperature and out-of-plane ferromagnetic order are in agreement with the experimental evidence. In addition, a uniaxial strain can induce a ferroelastic switching together with the magnetic easy axis, resulting in a strong intrinsic magnetoelasticity. Our results open up a new possibility for the realization of novel two-dimensional ferromagnets and provide a platform for understanding the underlying physical mechanism.