What if a single atomic sheet could be an antiferromagnetic semiconductor in its natural state, then become a half-metal under a magnetic field? This paper predicts exactly that behavior for MnSi2N4. Two-dimensional materials have a wide variety of electronic properties, including metallic, semi-metallic, semiconducting and insulating properties.

However, many two-dimensional materials lack intrinsic magnetism, such as graphene and MoS2, which motivates researchers to induce magnetism through defect engineering, adsorption or insertion of magnetic atoms. However, these schemes are difficult to construct stable. The electronic structure and magnetic properties of monolayer MnSi2N4 are explored based on first-principles calculations.

The results demonstrate that two-dimensional MnSi2N4 is a stable antiferromagnetic semiconductor in which the ground state is an antiferromagnetic state. The large magnetic exchange parameter indicates a strong antiferromagnetic coupling between the magnetic Mn atoms.

All calculations were conducted using the Vienna ab initio simulation package, or VASP. The projection augmented wave method was adopted to describe the interaction between ions and electrons, and the cutoff energy is set as five hundred electron volts.

The generalized gradient approximation of the Perdew–Burke–Ernzerhof form was employed to describe exchange correlation. An eighteen angstrom vacuum layer was added in the out-of-plane direction to eliminate interlayer interactions, and the Brillouin zone was sampled with a thirteen by thirteen by one k-point mesh.

The calculated cohesive energy of MnSi2N4 is negative five point zero three electron volts per atom, comparable to the value of the MoS2 monolayer and MoSi2N4. The phonon spectrum was calculated to check stability, and there is no imaginary phonon frequency throughout the Brillouin zone, indicating that the structure is dynamically stable.

Consequently, the MnSi2N4 monolayer has excellent stability and thus may be experimentally prepared. Figure two shows the phonon spectrum of monolayer manganese silicon two nitrogen four along the high-symmetry path from gamma to M, K, and back to gamma.

The plotted branches remain at or above zero frequency throughout this path, with no imaginary phonon frequencies visible. This matters because the absence of imaginary modes supports the dynamical stability of the proposed monolayer structure. The possible magnetic orderings were first determined as ferromagnetic and antiferromagnetic states.

The total energies of the antiferromagnetic and ferromagnetic phases are negative two hundred eighteen point six five zero electron volts and negative two hundred seventeen point six five eight electron volts, respectively. The energy of the antiferromagnetic state is lower than that of the ferromagnetic state, hence MnSi2N4 has an antiferromagnetic ground state.

In this case, the net magnetic moment is zero and the four manganese atoms in the supercell have an antiparallel magnetic state with the same magnetic moment of three point zero five Bohr magnetons. Figure three compares spin polarization in monolayer manganese silicon nitride.

Panels A and B map spin-up and spin-down charge densities using yellow and light-blue isosurfaces, while panels C and D schematically show the manganese spin orientations in the ferromagnetic and antiferromagnetic arrangements. This visual matters because it connects the spatial spin-density pattern with the competing magnetic configurations, supporting the authors’ identification of an antiferromagnetic ground state from total-energy calculations.

MnSi2N4 exhibits indirect semiconducting property without bands crossing the Fermi level. The conduction band minimum and the valence band maximum are located at the K point and M point, respectively. The band gap is small, at zero point two six electron volts, and the bands are degenerate with symmetrical total density of states for spin-up and spin-down states.

No states exist near the Fermi level along with a small energy gap. Figure four shows the antiferromagnetic band structure and total density of states of monolayer MnSi₂N₄, with spin-up in black and spin-down in red dotted lines. The bands do not cross the Fermi level, indicating an indirect semiconductor: the conduction-band minimum is at K, the valence-band maximum is at M, and the band gap is zero point two six electron volts.

The matching spin bands and symmetric density of states indicate spin degeneracy in this state. Strain is an effective means of manipulating electronic structure and magnetic properties, and it is widely utilized to modulate the electronic structure and magnetic properties of monolayer systems.

The strain is defined as the lattice constant difference divided by the relaxed lattice constant in the equilibrium state. The magnetic moment of the manganese atom remains about three Bohr magnetons per unit cell under strain. Figure seven shows how strain tunes two magnetic properties of monolayer manganese silicon nitride.

In panel A, the exchange parameter J changes across the strain range, while panel B tracks the magnetic anisotropy energy, defined as the in-plane energy minus the out-of-plane energy. The strain-free value is reported as minus three hundred forty-five microelectronvolts per manganese atom, indicating an in-plane easy axis; together, these curves show why strain is a useful control for magnetic behavior.

The electronic and magnetic properties of monolayer MnSi2N4 are explored based on first-principles calculations. Monolayer MnSi2N4 is an intrinsic antiferromagnetic semiconductor with a small indirect band gap of zero point two six electron volts. MnSi2N4 has strong antiferromagnetic coupling along with strong in-plane magnetocrystalline anisotropy energy.

MnSi2N4 is predicted to be a stable antiferromagnetic semiconductor with a small indirect band gap, strong antiferromagnetic coupling, and a field-driven half-metallic state that could matter for spintronic devices.