A family of high-temperature ferromagnetic monolayers with locked spin-dichroism-mobility anisotropy: MnNX and CrCX (X = Cl, Br, I; C = S, Se, Te)

Abstract

Two-dimensional magnets have received increasing attention since Cr2Ge2Te6 andCrI3 were experimentally exfoliated and measured in 2017. Although layered ferromagnetic metals were demonstrated at room temperature, a layered ferromagnetic semiconductor with high Curie temperature (Tc) is yet to be unveiled.Here, we theoretically predicted a family of high Tc ferromagnetic monolayers, namely MnNX and CrCX (X=Cl, Br and I; C=S, Se and Te). Their Tc values were predicted from over 100 K to near 500 K with Monte Carlo simulations using an anisotropic Heisenberg model. Eight members among them show semiconducting bandgaps varying from roughly 0.23 to 1.85 eV. These semiconducting monolayers also show extremely large anisotropy, i.e. ~10 1 for effective masses and ~10 2 for carrier mobilities, along the two in-plane lattice directions of these layers. Additional orbital anisotropy leads to a spin-locked linear dichroism, in different from previously known circular and linear dichroisms in layered materials. Together with the mobility anisotropy, it offers a spin-, dichroism-and mobility-anisotropy locking. These results manifest the potential of this 2D family for both fundamental research and high performance spin-dependent electronic and optoelectronic devices.

Strain‐Sensitive Magnetization Reversal of a van der Waals Magnet

“…DFT Calculations: Density functional theory calculations were performed using the same methods described in our previous publications. [51][52][53] In brief, a van der Waals density functional (vdW-DF) method was used, [54,55] with the optB86b functional [56] for the exchange part (optB86b-vdW) to optimize atomic structures of the bulk FGT, which usually reveals good agreements of calculated structure-related properties with experimental values of 2D materials. [57,58] Given optimized structures, the standard Perdew-Burke-Ernzerhof (PBE) functional was used [59] with consideration of spin-orbit coupling (SOC) to compare energy differences of all considered magnetic configurations; this scheme was found to share the qualitatively same results with the Heyd-Scuseria-Ernzerhof (HSE06) functional [60] in other magnetic 2D layers, e.g., CrI 3 [61] and CrSCl.…”

“…[57,58] Given optimized structures, the standard Perdew-Burke-Ernzerhof (PBE) functional was used [59] with consideration of spin-orbit coupling (SOC) to compare energy differences of all considered magnetic configurations; this scheme was found to share the qualitatively same results with the Heyd-Scuseria-Ernzerhof (HSE06) functional [60] in other magnetic 2D layers, e.g., CrI 3 [61] and CrSCl. [52] Density functional perturbation theory [62] was employed to calculate vibrational frequencies at the Gamma point (VASP). An on-site Coulomb interaction to the Fe 3d orbitals is considered with different U and J values: U = 3.6 eV and J = 0.2 eV for Fe 3+ and U = 4.6 eV and J = 1.0 eV for Fe 2+ , as revealed by a linear response method.…”

Quantum anomalous Hall effect in two-dimensional magnetic insulator heterojunctions

“…With FM state as the initial magnetic configuration, through an energy minimization and electron density optimization process, we identified 46 potential magnetic semiconductors (see Supplementary Table 1). 2D FM insulators MnNX and CrCX (X = Cl, Br, I; C = S, Se, Te) have been predicted in previous work [45][46][47][48] . Our comprehensive study puts this 2D compound family as a great platform for the discovery and design of quantum materials based on 2D magnetic heterojunctions.…”

Theoretical simulation and design of two-dimensional ferromagnetic materials

“…Wang 等人 [63] 进一步研究了CrCX(X=Cl, Br, I; C=S, Se, Te) 单层的铁磁性能, 发现CrSeBr的有效质量和载流子迁 移率表现出明显的各向异性(图4(f), (g)). Cr 2 I 3 X 3 (X=Br, Cl)单层也是一种间接带隙半导体, 具有本征的 铁磁性 [67] .…”

“…Copyright © 2018, American Chemical Society. (f), (g) 单层CrSeBr的电子结构以及Γ点的能带结构 [63] . Copyright © 2019, Elsevier Figure 4 (Color online) Two-dimensional Cr based ferromagnetic semiconductor.…”