Structural, electronic, and magnetic properties of CrTe2

Two-dimensional chromium ditelluride (CrTe2) is a promising ferromagnetic
layered material that exhibits long-range ferromagnetic ordering in the
monolayer limit. The formation energies of the different possible
structural phases (1T, 1H, 2H) calculated from density functional theory
(DFT) show that the 1T phase is the ground state, and the energetic
transition barriers between the phases, calculated by the nudged elastic
band method, are large, on the order of 0.5 eV. The self-consistent
Hubbard U correction parameters are calculated for all the phases of
CrTe2. The calculated magnetic moment of 1T-CrTe2 with ≥2 layers lies in
the plane, whereas the magnetic moment of a monolayer is out-of-plane.
Band filling and tensile biaxial strain cause the magnetic moment of a
monolayer to switch from out-of-plane to in-plane, and compressive biaxial
strain in a bilayer causes the magnetic moment to switch from in-plane to
out-of-plane. The magnetic anisotropy is shown to originate from the large
spin-orbit coupling (SOC) of the Te atoms and the anisotropy of the
exchange coupling constants Jxy and Jz in an XXZ type Hamiltonian.
Renormalized spin wave theory using experimental values for the magnetic
anisotropy energy and Curie temperatures provides a range of values for
the nearest neighbor exchange coupling.