Robust Antiferromagnetism of the 2H-FeSiN Monolayer with Correlation and Strain Effects.

A new class of Janus two-dimensional materials, MAN (M = V, Nb, Ta; A = Si, Ge), has recently been theoretically proposed, exhibiting the absence of magnetic ordering. However, the fundamental origin of this nonmagnetic behavior remains unresolved. In this work, we employ first-principles calculations to predict a new Janus 2D antiferromagnetic material, 2H-FeSiN. Our calculations reveal that 2H-FeSiN possesses intrinsic out-of-plane electric polarization with a dipole moment of 0.044 e·Å. In contrast to the nonmagnetic ground state found in 2H-VSiN, spin polarization calculations demonstrate that 2H-FeSiN has an integer magnetic moment of 3 μ/cell localized within its spin sublattice. This distinct spin polarization behavior between two systems is systematically explained through a combination of crystal field effect and Hund's rules. Utilizing the nearest-neighbor Heisenberg model, we identify an antiferromagnetic ground state with a Néel temperature of 180 K. Further investigations into correlation and strain effects reveal robust antiferromagnetic coupling between two sublattices, which persists under electronic correlation tuning and biaxial strain modulation. These findings not only present a stable 2D antiferromagnetic candidate but also elucidate the effects of electronic correlation and strain in governing its electronic and magnetic properties.