Magnetic monolayer Li₂N: Density Functional Theory calculations

Abstract

-Density functional theory (DFT) calculations are used to investigate the electronic and magnetic structures of a two-dimensional (2D) monolayer Li2N. It is shown that bulk Li3N is a non-magnetic semiconductor. The non-spin-polarized DFT calculations show that p electrons of N in 2D Li2N form a narrow band at the Fermi energy EF due to a low coordination number, and the density of states at the Fermi energy (g(EF)) is increased as compared with bulk Li3N. The large g(EF) shows instability towards magnetism in Stoner's mean-field model. The spinpolarized calculations reveal that 2D Li2N is magnetic without intrinsic or impurity defects. The magnetic moment of 1.0 μB in 2D Li2N is mainly contributed by the pz electrons of N, and the band structure shows half-metallic behavior. Dynamic instability in planar Li2N monolayer is observed, but a buckled Li2N monolayer is found to be dynamically stable. The ferromagnetic (FM) and antiferromagnetic (AFM) coupling between the N atoms is also investigated to access the exchange field strength. We found that planar (buckled) 2D Li2N is a ferromagnetic material with Curie temperature Tc of 161 (572) K. editor's choice Copyright c EPLA, 2017Introduction. -Currently, huge research efforts are undertaken to explore new 2D materials for a wide range of applications [1][2][3][4][5]. It is well known from semiconductor physics that reduced dimensionality not only affects the electronic structure [6] and the electronic density of states (DOS) near the Fermi energy, but also the electronic dispersion relations [7]. This effect of the dimensionality is particularly strong in 2D materials which, by definition, consist of a sheet only few atomic layers in thickness. Due to quantum confinement, the electronic bands in the remaining two in-plane directions can display metallic, insulating, or semiconducting behavior even at variance with the behavior in the 3D bulk compound from which they were derived [8][9][10][11][12][13][14][15]. In some cases, 2D materials have very unique electronic properties, i.e., Dirac cones in graphene, silicene, etc. [8,16]. There are also 2D magnetic materials, e.g., transition metal nitrides, where magnetism is due to d electrons [17,18]. Recently, magnetism has been predicted [19] and confirmed experimentally in a 2D compound of chromium [20]. In contrast, our present theoretical work predicts the possibility of 2D magnetism even in the absence of d electrons.

Defects-driven magnetism in bulk α-Li3N

“…Bulk Li 3 N possesses an ionic nature with maximum charge concentrated around the N sites and a slight charge distribution observed near the Li sites. 33 The calculated spin-polarized total and atomprojected (P) density of states (DOS),(see Ref. 33), reveal the absence of exchange splitting, which is a sign of nonmagnetic behavior.…”

“…33 The calculated spin-polarized total and atomprojected (P) density of states (DOS),(see Ref. 33), reveal the absence of exchange splitting, which is a sign of nonmagnetic behavior. These results confirm that bulk Li 3 N has a non-magnetic and semiconducting character in its pure form which is consistent with the previous results.…”

“…32 Very recently we also observed magnetism in the Li 2 N monolayer without any crystal defects. 33 α-Li 3 N has a unique hexagonal crystal structure with four atoms per unit cell, at ambient conditions and equilibrium pressure [ Fig. 1].…”

Two-dimensional antiferromagnetic semiconductor T'-MoTeI from first principles

“…2D magnetic semiconductors are of great potential for applications in low-dimensional spintronic devices because of their magnetic and semiconducting properties [6,7]. Many 2D magnetic materials have been predicted so far, and some have been successfully prepared in experiments [8][9][10][11][12]. Because antiferromagnetic (AFM) semiconductors have stability under magnetic-field perturbations and large magnetotransport effects, 2D AFM semiconductors boast tremendous advantages in carrier injection, detection, sensors, and magnetic storage [13], but only a few 2D AFM semiconductors, such as Fe 2 Cl 3 I 3 , FePS 3 , and CoS 2 , have been reported so far [14][15][16][17][18][19].…”

CrAs Monolayer: Low Buckled 2D Half‐Metal Ferromagnet

“…Hence, it is quite natural to search for intrinsic ferromagnetic (FM) 2D materials for possible usages in carrier injection, detection, sensors, magnetic storage, and emergent heterostructure devices. The quest for 2D FM materials 16 is very young and efforts are under way to discover new intrinsic FM materials that can replace the conventional bulk magnetic materials.…”