Two‐dimensional (2D), high‐temperature, half‐metal ferromagnetic semiconductors with large spin gap and topological band structures are highly desirable for novel nanoscale spintronic applications. A family of stable 2D honeycomb‐Kagome Cr2X3 (X=O,S,Se) monolayers is proposed through first‐principles calculations. Buckled Cr2O3 is a ferromagnetic semiconductor with large out‐of‐plane magnetocrystalline anisotropy energy and a predicted Curie temperature of 332 K under moderate biaxial tensile strain. Planar Cr2S3 and Cr2Se3 are ferromagnetic half‐metals with mirror‐symmetry‐protected nodal lines for spin‐down channel and large direct gap (4.59 and 4.76 eV) for spin‐up channel. The Fermi velocities for Cr2S3 and Cr2Se3 are 2.1×105 and 1.5×105 m s−1, respectively, which is comparable with that of silicene, 5.3 × 105 m s−1. Their Berezinskii–Kosterlitz–Thouless transition temperatures are determined to be as high as 445 and 695 K. In addition, their half metallicity can be well maintained on h‐BN nanosheets and is immune to chemical perturbation and mechanical strain. Its fascinating magnetic properties and topological nodal lines render 2D Cr2X3 (X=O,S,Se) suitable for novel spintronic devices and exotic quantum applications.
Some key technologies of real-time precise point positioning (PPP) are discussed in this paper and the mathematic model and method for estimating precise clock correction in real time is introduced. The realtime observations obtained from GPS continuous operational reference stations are used to estimate the accurate real-time satellite clock corrections. Comparison between the estimated satellite clock correction and final precise clock correction published by CODE indicates that RMS of the difference between each other is better than 0.2 ns. With the high accuracy real-time clocks, real-time PPP can be performed. The results show that the positioning accuracy of real-time PPP is about 5 cm in horizontal and 10 cm in vertical after a short period of initialization, which can satisfy the requirement of real-time user at this accuracy level. GPS observations from Wenchuan earthquake are also processed with the proposed method; the result shows that the surface coseismic displacement caused by the earthquake can be detected by real-time PPP method.
In article number 1900490, Fang‐Ping Ouyang, Xiang Xiong, and co‐workers propose a family of stable 2D honeycomb Kagome Cr2X3 (X=O,S,Se) monolayers through first‐principles calculations. Planar Cr2S3 and Cr2Se3 are ferromagnetic half‐metals with mirror symmetry protected nodal lines for spin‐down channels, while buckled Cr2O3 layers are ferromagnetic semiconductors with large out‐of‐plane magnetocrystalline anisotropy energy (MAE), and predicted Curie temperatures of 332 K under moderate biaxial tensile strain. These properties make such materials suitable for novel spintronic devices and exotic quantum applications.
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