posted on 2023-01-09, 23:03authored byDaniel Wines, Kamal Choudhary, Francesca Tavazza
The
search for two-dimensional (2D) magnetic materials has attracted
a great deal of attention because of the experimental synthesis of
2D CrI3, which has a measured Curie temperature of 45 K.
Often times, these monolayers have a higher degree of electron correlation
and require more sophisticated methods beyond density functional theory
(DFT). Diffusion Monte Carlo (DMC) is a correlated electronic structure
method that has been demonstrated to be successful for calculating
the electronic and magnetic properties of a wide variety of 2D and
bulk systems, since it has a weaker dependence on the Hubbard parameter
(U) and density functional. In this study, we designed
a workflow that combines DFT+U and DMC in order to treat 2D correlated
magnetic systems. We chose monolayer CrX3 (X = I, Br, Cl,
F), with a stronger focus on CrI3 and CrBr3,
as a case study due to the fact that they have been experimentally
realized and have a finite critical temperature. With this DFT+U and
DMC workflow and the analytical method of Torelli and Olsen, we estimated
a maximum value of 43.56 K for the Tc of CrI3 and 20.78 K for the Tc of CrBr3, in addition to
analyzing the spin densities and magnetic properties with DMC and
DFT+U. We expect that running this workflow for a well-known material
class will aid in the future discovery and characterization of lesser
known and more complex correlated 2D magnetic materials.