A 2D ferromagnetic semiconductor in monolayer Cr-trihalide and its Janus structures

Using first principles calculations, we explored the physical properties of two-dimensional (2D) Cr-trihalide X3-Cr2-X3 or CrX3 (X = Cl, Br, I) and its Janus monolayers X3-Cr2-Y3 (X and Y = Cl, Br, I) where X ≠ Y. We found that Janus monolayer X3-Cr2-Y3 materials are dynamically stable and that it i...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2018, Vol.20 (33), p.21755-21763
Main Authors: Moaied, Mohammed, Lee, Jiyoul, Hong, Jisang
Format: Article
Language:English
Subjects:
Computer simulation
Dependence
Dielectric strength
Dipole moments
Electronegativity
Ferromagnetism
First principles
Halides
Mathematical analysis
Monolayers
Physical properties
Refractivity
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Summary:Using first principles calculations, we explored the physical properties of two-dimensional (2D) Cr-trihalide X3-Cr2-X3 or CrX3 (X = Cl, Br, I) and its Janus monolayers X3-Cr2-Y3 (X and Y = Cl, Br, I) where X ≠ Y. We found that Janus monolayer X3-Cr2-Y3 materials are dynamically stable and that it is feasible to synthesize X3-M2-Y3 2D-crystals. Both pristine and Janus layers have intrinsic two-dimensional ferromagnetic semiconducting band structures; the largest band gap of 2.3 eV was found in Cl3-Cr2-Cl3, while the band gaps decreased in heavier halide systems. Using Monte Carlo simulations, we found that the Curie temperatures (Tc) showed the same feature of strong dependence on the X and Y halides. In non-polar systems with X = Y, we found no dipole moment, while the polar systems with X ≠ Y had induced dipole moments. Thus, the pristine layer has the same function on both sides, while the Janus layer displays dissimilar work functions in two different surface directions; this was related to the dipole moment and the value of electronegativity. We found that both pristine and Janus layer systems displayed rather weak frequency-dependent dielectric functions. Thus, the variation of the refractive index with frequency was small, and almost zero reflectivity was found in all systems.
ISSN:1463-9076
1463-9084
DOI:10.1039/c8cp03489c