Tunable Magnetism in 1T-CrTe₂ Due to Competing Charge and Spin Density Waves

Long-range order magnetism in 2D materials is an active field of research given its potential applications especially due to its promise in spintronic devices. 1T-CrTe₂ is a promising candidate for intrinsic 2D magnetism at high temperatures and has experimentally exhibited both ferromagnetic (FM) and anti-ferromagnetic (AFM) orderings. In this work, we applied density functional theory to investigate the lattice dynamics, electronic and magnetic properties of monolayer 1T-CrTe₂ in both magnetic orderings as well as their dependences on lattice parameters. We found that the ground state of monolayer 1T-CrTe₂ possesses an AFM state. By varying the lattice parameters between 3.4 °A and 3.8 °A, we obtain a phase diagram of the transition between FM to AFM state. The transition from the AFM to FM is associated with larger lattice parameters, in agreement with the experimental observations. In addition to the previously reported charge density wave (CDW), we found the possible emergence of a commensurate spin density wave (SDW) with a modulation period of ? = 7.17 °A. The SDW opens up a gap at the Fermi level as seen from the band structure. The formation of the SDW is attributed to the interactions between the p, t2g, and eg orbitals, leading to the formation of a Fermi nesting vector within the Fermi surface. In light of our results, the AFM and FM states in 1T-CrTe2 can be understood in terms of the competing charge and spin density waves.