Strain‐Induced Magnetism in MSi₂N₄ (M = V, Cr): A First‐Principles Study

Abstract

The discovery of ferromagnetic 2D van der Waals (vdW) materials has opened up opportunities for exploring and harnessing magnetism in low‐dimensional limit, and developing innovative paper‐like spintronic devices. Stress engineering demonstrates unique advantages in regulating material properties, especially for 2D materials. With the aid of first‐principles calculations, the effectiveness of strain engineering for modulating the electronic and magnetic properties of MSi2N4 (M = V, Cr) monolayers from a new family of layer‐structured 2D vdW materials is explored. Their magnetic configurations are effectively tuned via the uniaxial and biaxial tensile strain of in‐plane lattice vectors. VSi2N4 exhibits half‐metallic ferromagnetic character, whereas CrSi2N4 is prone to be antiferromagnetic (AFM), which is rationalized from the competition between the direct metal–metal AFM interaction and the 900 ferromagnetic superexchange. More intriguingly, VSi2N4 demonstrates a high magnetic ordering temperature of 285 K, which is close to room temperature. The predicted appealing properties of VSi2N4 under strain await experimental confirmation.

Stable ferromagnetism and high Curie temperature in VGe2N4

“…It is seen that the heavier the element for Z, the larger the lattice constant is, and the influence is more obvious for out-of-plane lattice c. In the VN 2 layer, each V atom is coordinated with six N atoms, forming a perfect triangular prism. The V-N bond length is 2.070 Å, slightly larger than that in VSi 2 N 4 (2.040 Å) [25], which produces different magnetic evolution under strain. In the upper and bottom outer Ge-N layer, a Ge atom coordinates to four N atoms, which leads to tetrahedron environment.…”

“…Since reported, the MA 2 Z 4 (M = transition metals; A = IVA elements; Z = VA elements) family, as another milestone, has sparked a wide range of intriguing following studies. Not only the family has been enriched by predictions of new members such as MA 2 Z 4 (M = Ti, V, Cr; A = Si; Z = N, P, As), but also compositional/structural tailoring has been proposed to satisfy practical requirements [8,[18][19][20][21][22][23][24][25][26][27]. In the contribution, Zhong et al revealed that under external strain, MSi 2 N 4 (M = Ti, Cr, Mo) undergoes a phase transition which is attributed to the asymmetric charge transfer [8].…”

Stable Ferromagnetism and High Curie Temperature in VGe$_2$N$_4$

“…It is seen that the heavier the element for Z, the larger the lattice constant is, and the influence is more obvious for out-of-plane lattice c. In the VN 2 layer, each V atom is coordinated with six N atoms, forming a perfect triangular prism. The V-N bond length is 2.070 Å, slightly larger than that in VSi 2 N 4 ( 2.040 Å) 21 . In the upper and bottom outer Ge-N layer, a Ge atom coordinates to four N atoms, which leads to tetrahedron environment.…”

“…Since reported, the MA 2 Z 4 (M= transition metals; A=IVA elements; Z=VA elements) family, as another milestone, has sparked a wide range of intriguing following studies. Not only the family has been enriched by predictions of new members such as MA 2 Z 4 (M=Ti, V, Cr; A=Si; Z=N, P, As), but also compositional/structural tailoring has been proposed to satisfy practical requirements 8,[16][17][18][19][20][21] . In the contribution, Zhong et al revealed that under external strain, MSi 2 N 4 (M=Ti, Cr, Mo) undergoes a phase transition which is attributed to the asymmetric charge transfer 8 .…”

Electronic and Excitonic Properties of MSi2Z4 Monolayers

“…Depending on the space group, as well as the number of valence electrons, 1L MA 2 Z 4 can be non-magnetic or ferromagnetic semiconductors or metals, some of which exhibit topological and superconducting behavior. [7] Numerous properties of 1L MA 2 Z 4 have been predicted by DFT calculations, including robust magnetic properties, [9][10][11] defect-induced half-metalicity, [12] high piezoelectric coefficients, [13][14][15][16][17][18] ferroelectricity switchable via interlayer sliding, [19] high intrinsic lattice thermal conductivity, [20][21][22] exceptional thermoelectric performance, [23][24][25] anomalous spin and valley Hall effects, [7,9,[26][27][28] Ising superconductivity, [7] giant tunneling magnetoresistance, [29] tunable absorption coefficient, [30] and effective chemical adsorption properties. [31][32][33] Large on/off ratios were obtained in simulations of 1L MA 2 Z 4 transistors.…”