Intrinsic multiferroicity in two-dimensional VOCl<sub>2</sub> monolayers

Ai, Haoqiang; Song, Xiaohan; Qi, Siyun; Liu, Weifeng; Zhao, Mingwen

doi:10.1039/c8nr08270g

Cited by 70 publications

(79 citation statements)

References 68 publications

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“…Therefore, developing new materials and exploring their anisotropic physical properties and functional devices are of great significance to the development of science and technology.Recently, layered transition metal oxide dihalides MOX 2 (M = V, Nb, Ta, Mo; X = Cl, Br, I) have gained increasing attention among materials scientists due to their chiral crystal structure and unique physical properties. [28][29][30][31][32][33] Among them, NbOI 2 has a low-symmetry monoclinic structure (space group C2), in which Nb atoms shift away from the center of [NbO 2 I 4 ] octahedra connected by sharing I-I edges and cornered O atoms along the c-and b-axes. Various connection modes enable NbOI 2 strong anisotropic physical properties and highly dispersed band structure.…”

mentioning

confidence: 99%

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Fang

Wang

et al. 2021

Advanced Materials

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induced diodes, [23,24] polarization-sensitive photodetectors, [25,26] synaptic-neuromorphic devices, [27] etc. Although the research on anisotropic 2D materials is progressing rapidly, it is still in its infancy as a whole. Therefore, developing new materials and exploring their anisotropic physical properties and functional devices are of great significance to the development of science and technology.Recently, layered transition metal oxide dihalides MOX 2 (M = V, Nb, Ta, Mo; X = Cl, Br, I) have gained increasing attention among materials scientists due to their chiral crystal structure and unique physical properties. [28][29][30][31][32][33] Among them, NbOI 2 has a low-symmetry monoclinic structure (space group C2), in which Nb atoms shift away from the center of [NbO 2 I 4 ] octahedra connected by sharing I-I edges and cornered O atoms along the c-and b-axes. Various connection modes enable NbOI 2 strong anisotropic physical properties and highly dispersed band structure. The simulated optical absorption coefficient along the c-axis (α c ) is an order of magnitude higher than that along the b-axis (α b ). [34] Consequently, the NbOI 2 is expected to exhibit unique in-plane anisotropy. However, until now, the preparation and basic properties of 2D NbOI 2 crystals have not been thoroughly investigated, and in particular, the in-plane anisotropy caused by its low-symmetry structure is still unclear.Here, we introduce a kind of transition metal oxide dihalides, NbOI 2 , into the 2D materials family with experimental demonstration of strong in-plane anisotropy. Few-layer and monolayer NbOI 2 crystals were obtained through mechanical exfoliation, and these crystals showed large second harmonic generation (SHG) response, verifying its noncentrosymmetric crystal structure. The strong in-plane anisotropy of phonon vibration in 2D NbOI 2 crystals was observed by using angleresolved polarized Raman measurements. The anisotropic electronic dispersion around the Fermi surfaces leads to the strong anisotropy of optical absorbance with an anisotropic factor of 1.75. In addition, highly anisotropic in-plane electrical resistance with a factor of 1.34 and photoresponsivity with a factor of 1.7 were demonstrated in 2D NbOI 2 crystals. These findings indicate that the 2D NbOI 2 crystal can serve as a promising candidate in anisotropic electronic and optoelectronic devices. Results and DiscussionBulk NbOI 2 belongs to the monoclinic space group C2 (No. 5) with a = 15.18 Å, b = 3.92 Å, c = 7.52 Å, β = 105.5°. Figure 1a Exploring in-plane anisotropic 2D materials is of great significance to the fundamental studies and further development of polarizationsensitive optoelectronics. Herein, chiral niobium oxide diiodide (NbOI 2 ) is introduced into the intriguing anisotropic 2D family with the experimental demonstration of anisotropic optical and electrical properties. 2D NbOI 2 crystals exhibit highly anisotropic dispersed band structures around the Fermi surface and strong in-plane anisotropy of phonon vibrations owing to the diff...

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confidence: 99%

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Fang

Wang

et al. 2021

Advanced Materials

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“…Antiferromagnetism and ferroelasticity were demonstrated in single‐layer AgF 2 semiconductor, which show a high transition signal and low ferroelastic switching barrier 122 . The VOCl 2 monolayer 123 and VS 2 bilayer 124 were explored as antiferromagnetic and ferroelectric semiconductors. The 2D group IV monochalcogenides (GeS, GeSe, SnS, and SnSe) 125 and silver/copper monohalides (CuCl, AgCl, AgBr, AgI, and CuBr) 126 were predicted to be multiferroic materials with spontaneous ferroelectricity and ferroelasticity, showing potential applications in 2D mechano‐opto‐electronic and memory devices.…”

Section: Two‐dimensional Magnetismmentioning

confidence: 99%

Computational design of two‐dimensional magnetic materials

Miao

Sun

2021

WIREs Comput Mol Sci

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As a long‐standing research topic in materials physics and chemistry, magnetic materials have been receiving increasing attention for their applications in spintronic devices, such as spin field‐effect transistor and data‐storage memory. Two‐dimensional (2D) magnets are a family of emerging magnetic materials with atomically thin thickness, which can be easily integrated into heterostructural devices, providing incredible possibility for understanding 2D magnetism and great potential for applications in future ultrathin spintronic devices. Recent effort from theory, simulations and experiments has made notable progress on 2D magnets and devices, especially on 2D van der Waals materials and heterojunctions. Here theoretical advances using physical models and computational approaches on the study of new 2D magnets and devices are briefly summarized and possible directions for future investigation are extensively discussed, which may inspire growing interest on the development and applications of 2D magnets and spintronic devices. This article is categorized under: Structure and Mechanism > Computational Materials Science Electronic Structure Theory > Density Functional Theory

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“…8 c [ 121 ]. Similarly, a VOCl 2 monolayer was predicted to possess a large intrinsic in-plane spontaneous polarization of 312 pC/m and stable antiferromagnetism with a Néel temperature as high as ∼177 K [ 122 ]. The V off-center displacement that contributes to ferroelectricity can be ascribed to the pseudo Jahn–Teller distortion, while the magnetism stems from the V ion too.…”

Section: D Multiferroicsmentioning

confidence: 99%

Single-phase multiferroics: new materials, phenomena, and physics

Lin

et al. 2019

National Science Review

152

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Multiferroics, where multiple ferroic orders coexist and are intimately coupled, promise novel applications in conceptually new devices on one hand, and on the other hand provide fascinating physics that is distinctly different from the physics of high-TC superconductors and colossal magnetoresistance manganites. In this mini-review, we highlight the recent progress of single-phase multiferroics in the exploration of new materials, efficient roadmaps for functionality enhancement, new phenomena beyond magnetoelectric coupling, and underlying novel physics. In the meantime, a slightly more detailed description is given of several multiferroics with ferrimagnetic orders and double-layered perovskite structure and also of recently emerging 2D multiferroics. Some emergent phenomena such as topological vortex domain structure, non-reciprocal response, and hybrid mechanisms for multiferroicity engineering and magnetoelectric coupling in various types of multiferroics will be briefly reviewed.

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Intrinsic multiferroicity in two-dimensional VOCl₂ monolayers

Abstract: The coexistence of ferroelectricity and magnetism in VOCl2 monolayer which is mechanically strippable from the bulk material offers a tantalizing potential for high-density multistate data storage.

Cited by 70 publications

References 68 publications

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Computational design of two‐dimensional magnetic materials

Single-phase multiferroics: new materials, phenomena, and physics

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Intrinsic multiferroicity in two-dimensional VOCl2 monolayers

Abstract: The coexistence of ferroelectricity and magnetism in VOCl2 monolayer which is mechanically strippable from the bulk material offers a tantalizing potential for high-density multistate data storage.

Cited by 70 publications

References 68 publications

2D NbOI2: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

2D NbOI2: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Computational design of two‐dimensional magnetic materials

Single-phase multiferroics: new materials, phenomena, and physics

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Intrinsic multiferroicity in two-dimensional VOCl₂ monolayers

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties