Fig.1 Theoretical prediction of new magnetic materials. a: The Tc of twelve magnetic single-layer materials is predicted to reach 100K to 500K. b: Strong anisotropy with spin-, dichroism- and mobility-anisotropy locking. c: CrOCl bulk phase magnetic ground state. d-e: The computational simulation is highly consistent with the experimentally measured anisotropic Raman diagrams.
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Science Bulletin
A family of high-temperature ferromagnetic monolayers with locked spin-dichroism-mobility anisotropy: MnNX and CrCX (X = Cl, Br, I; C = S, Se, Te)
The search for room temperature ferromagnetic semiconductors is one of 125 important questions posed in Science. In previous studies, researchers found that strong electron doping (1 e/Cr) of CrS2 can lead to its transformation from AFM metal to FM semiconductor, and replacing S with Cl atoms to form CrSCl monolayer is one of the feasible ideas to realize such doping.
Based on the above thought, 12 kinds of single-layer ferromagnetic materials with high Tc are predicted: MnNX and CrCX (where X=Cl,Br,I; C=S,Se,Te)[1]. Based on the anisotropic Heisenberg model and renormalized spin wave theory, Tc of this series of materials is predicted to range from 100K to 500K (Figure 1a). Eight members among them show semiconducting bandgaps varying from roughly 0.23 to 1.85 eV. These semiconducting monolayers also show extremely large anisotropy 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 (Figure 1b).
The work was published in Sci.Bull. 2019, making it one of the 10 most downloaded articles of that year. The material predictions has been verified and cited by several different experimental groups in Nat. Mat (1 paper), Nat. Nanotech. (2 papers), Adv. Mater. (2 papers) and Nano Letters (1 paper). The magnetic properties and anisotropic electronic structure were confirmed to be consistent with our theoretical prediction.
On this basis, the researchers, in collaboration with experimental collaborators, determined the bulk phase magnetic ground state and magnetic field evolution of CrOCl[2] (FIG. 1c-e). Combined with the magnetic transport measurements of experimental collaborators, the layered dependent magnetic field evolution behavior of the CrSBr system was investigated[3].
1. Wang, C. et al. A family of high-temperature ferromagnetic monolayers with locked spin-dichroism-mobility anisotropy: MnNX and CrCX (X = Cl, Br, I; C = S, Se, Te). Science Bulletin 64, 293-300 (2019)
2. Gu, P. et al. Magnetic Phase Transitions and Magnetoelastic Coupling in a Two-Dimensional Stripy Antiferromagnet. Nano Letters 22, 1233-1241 (2022)
3. Ye, C. et al. Layer-Dependent Interlayer Antiferromagnetic Spin Reorientation in Air-Stable Semiconductor CrSBr. ACS Nano 16, 11876-11883 (2022)