TMN (TM = V, Cr, Mn, Fe, Co) monolayers \-- a new class of non-van der Waals 2D magnets

Abstract

We have systematically examined various parameters of t- (tetragonal) and h- (hexagonal) lattices of transition metal nitride (TMN) monolayers through first-principles calculations, emphasising their structural and magnetic properties. Our study reveals that all TMN monolayers exhibit a preference for a magnetic ground state. Employing the Heisenberg model, we extract exchange interaction and magnetic anisotropy parameters. Notably, half of the structures exhibit a ferromagnetic (FM) configuration, while the remaining half adopt an antiferromagnetic (AFM) configuration. The magnetic anisotropy energy per metal atom falls within the range of 43 to 633 μeV for h-MnN and h-CoN, respectively. Monte Carlo (MC) simulations predict Curie and Néel temperatures for these monolayers, with T_C for h-MnN estimated at approximately 339 K. To better understand structural dynamics, we employ the variable-cell nudged elastic band (VC-NEB) method, which provides an activation energy E_a for the transition in CrN of about 1.22 eV. These findings highlight the potential applicability of these structures in magnetic and spintronic devices.