Single-layer metal halides MX<sub>2</sub> (X = Cl, Br, I): stability and tunable magnetism from first principles and Monte Carlo simulations

Kulish, Vladimir; Huang, Wei

doi:10.1039/c7tc02664a

Cited by 279 publications

(235 citation statements)

References 76 publications

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“…The apparent height of the zigzag phase is 0.34 Å smaller than that of the dot phase (inset of Figure 3a). Figure 3b and 26,27 The reduced thickness compared with CrI3 also imply the formation of single-layer CrI2 (interlayer distance, 6.77 Å). 26,27 Figure 3c shows the atomic-resolution STM image of single-layer CrI2, from which one can find that the topmost atoms in two symmetric directions is arranged uniformly, while the atomic arrangement in the third symmetric direction is wavy.…”

Section: Resultsmentioning

confidence: 97%

“…Figure 3b and 26,27 The reduced thickness compared with CrI3 also imply the formation of single-layer CrI2 (interlayer distance, 6.77 Å). 26,27 Figure 3c shows the atomic-resolution STM image of single-layer CrI2, from which one can find that the topmost atoms in two symmetric directions is arranged uniformly, while the atomic arrangement in the third symmetric direction is wavy. This implies that the zigzag superstructure may originate from the mismatch of the CrI2 lattice with the underlying Au(111) surface.…”

Section: Resultsmentioning

confidence: 97%

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Single-layer CrI3 grown by molecular beam epitaxy

Wang

Zhang

et al. 2020

Science Bulletin

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Single-and few-layer chromium triiodide (CrI3), which has been intensively investigated as a promising platform for two-dimensional magnetism, was usually prepared by mechanical exfoliation. Here, we report on the growth of single-layer CrI3 by molecular beam epitaxy under ultrahigh vacuum. The atomic structures and local density of states have been revealed by scanning tunneling microscopy (STM). Iodine trimers, each of which consists of three I atoms surrounding a three-fold Cr honeycomb center, have been identified as the basic units of the topmost I layer. Different superstructures of single-layer CrI3 with characteristic periodicity around 2-4 nm were obtained on Au(111), but only pristine structure was observed on graphite.At elevated temperatures (423 K), CrI3 was partially decomposed, resulting in the formation of single-layer chromium diiodide. Our bias-dependent STM images suggest that the unoccupied and occupied states are distributed spatial-separately, which is consistent with our density functional theory calculations. The effect of charge distribution on the superexchange interaction in single-layer CrI3 was discussed.Keywords: two-dimensional magnetic materials, CrI3, molecular beam epitaxy, scanning tunneling microscopy 2 / 18 Two-dimensional (2D) magnetic materials, which serve as ideal platforms for investigating spin-related emergent phenomena at reduced dimensions and exhibit potential applications in optoelectronics and spintronics, 1,2 have long been sought. However, as revealed by Mermin-Wagner theorem, long-range magnetic order in 2D systems with isotropic local magnetic interactions are thermodynamically instable at finite temperatures owing to enhanced thermal fluctuations. 3 By introducing magnetic anisotropy, on the other hand, 2D magnetism may exist in a number of layered van der Waals (vdW) materials, for example, transition metal chacogenides and halides. 4-6 Among them, single-and bi-layer chromium triiodide (CrI3) has been recently confirmed with intralayer ferromagnetism (FM) and interlayer antiferromagnetism (AFM). 7,8 The FM coupling in single-layer CrI3, which exhibits a Curie temperature of 45 K, slightly lower than that of the bulk counterpart (61 K), is mainly ascribed to the superexchange interaction between the neighboring Cr atoms mediated by the bridging I atoms. 9 The easy magnetization direction is out of plane with an anisotropy energy about 0.50-0.69 meV/Cr, according to density functional theory (DFT) calculations. 10,11 The magnetic tunneling junction consisting of four-layer CrI3 sandwiched with two graphene layers as the electrodes performs a magnetoresistance change as large as 19,000%, 12 demonstrating the advantages of layered vdW materials for fabricating advanced spintronic devices. [12][13][14][15] Besides CrI3, other layered materials, such as Cr2Ge2Te6, CrCl3, CrBr3, Fe3GeTe2 and FePS3, have been already obtained and verified with long-range magnetic order. [16][17][18][19][20][21] So far, mechanical exfoliation is the major method for preparing 2D magn...

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 97%

Single-layer CrI3 grown by molecular beam epitaxy

Wang

Zhang

et al. 2020

Science Bulletin

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“…The GKA rules have acquired success in explaining magnetic properties on an amount of two-dimensional (2D) and bulk materials, e.g. recently highlighted 2D materials of CrX 3 (X=F, Cl, Br, I) [8][9][10], ABX 3 (A=Mn, Cr; B=P, Si, Ge; X=S, Se, Te) [11], and bulk materials of AX 2 (A=V, Cr, Mn; X=Cl, Br, I) [12], AO 2 and BCl 3 (A=Mn, Cu, Ni; B=Co, Ni, Cu) [13,14], etc. While isolated counterexamples (e.g.…”

Section: Introductionmentioning

confidence: 99%

Super-exchange theory for polyvalent anion magnets

Zhang

Kong²,

Pang

et al. 2019

New J. Phys.

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The Goodenough-Kanamori-Anderson (GKA) rules have been widely applied for explaining the magnetic properties induced by super-exchange interaction. As conclusions of the super-exchange theory, they reveal the antiferromagnetic (ferromagnetic) ordering along with bond angle of 180°( 90°) in the cation-anion-cation interaction path, in which the theory sets a pre-condition that the electronic states of cations in all paths are identical. We observed that the GKA rules are in fact not universal and even invalid to materials containing anions with different valence states, for example, the layered CrOCl crystal (with two valence states of anions: O 2− and Cl − ). In this study, we propose an extended super-exchange theory (ESET) related to superposed electronic states of cation in a specific path. ESET is capable of predicting not only the sign and relative magnitude of magnetic exchange constants in different cation-anion-cation paths, but also the magnetic ground state. Through our proposed theory, we conclude that the magnetic ordering along with bond angle of 90°i n Cr-Cl-Cr path is moderately antiferromagnetic and of 180°in Cr-O-Cr path is strongly ferromagnetic, which are opposite to the contents of GKA rules. Moreover, we clarify that monolayer CrOCl has antiferromagnetic ordering rather than ferromagnetic as reported recently. The reliability of ESET is verified via first-principles calculation and previous experimental report as well, and its universality is also demonstrated. Thus, our theory is powerful to predict the magnetic properties, which makes it possible to design new high Curie temperature two-dimensional semiconducting ferromagnets with polyvalent anion materials.In order to get magnetic constants through first-principles calculation, we express the total energy of one magnetic atom for four configurations (figure 3) by Heisenberg Spin Hamiltonian [21] E E J J J S E E J J S 4

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“…The hotter topic in the scientific community is atomically thin materials with ferromagnetic properties. Recent theoretical predictions and experimental syntheses of ferromagnetic flat materials opened up new possibilities for their use in spintronic devices. Several years ago, it was theoretically predicted that a cis ‐semi‐hydrated graphene sheet ( cis ‐C 2 H) is ferromagnetic .…”

Section: Introductionmentioning

confidence: 99%

Computational Prediction of the Low‐Temperature Ferromagnetic Semiconducting 2D SiN Monolayer

Tkachenko

Song

Стегленко

et al. 2019

Physica Status Solidi (b)

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Since the discovery of graphene, 2D materials have captured the minds of scientists because of their attractive and unique electronic properties. In particular, magnetic 2D materials have become a subject of extensive discussions today. Using density functional theory calculations, it is shown that 2D SiN sheet (built out of nonmetallic main group atoms) is a ferromagnetic semiconducting material with a magnetic moment 1 μB per unit cell and an indirect bandgap of 1.55 eV. Calculated phonon spectrum and conducted ab initio molecular dynamics simulation reveal thermal and dynamical stability of the designed material. It is shown that the ferromagnetic state is stable up to 20 K. Magnetism of silicon mononitride can be described by the presence of an unpaired electron located on silicon atoms. The semiconducting and ferromagnetic properties of SiN monolayer open many opportunities for its potential use in spintronic and nanoelectronic devices.

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Single-layer metal halides MX₂ (X = Cl, Br, I): stability and tunable magnetism from first principles and Monte Carlo simulations

Abstract: We present a computational study on a novel class of single-layer materials.

Cited by 279 publications

References 76 publications

Single-layer CrI3 grown by molecular beam epitaxy

Single-layer CrI3 grown by molecular beam epitaxy

Super-exchange theory for polyvalent anion magnets

Computational Prediction of the Low‐Temperature Ferromagnetic Semiconducting 2D SiN Monolayer

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Single-layer metal halides MX2 (X = Cl, Br, I): stability and tunable magnetism from first principles and Monte Carlo simulations

Abstract: We present a computational study on a novel class of single-layer materials.

Cited by 279 publications

References 76 publications

Single-layer CrI3 grown by molecular beam epitaxy

Single-layer CrI3 grown by molecular beam epitaxy

Super-exchange theory for polyvalent anion magnets

Computational Prediction of the Low‐Temperature Ferromagnetic Semiconducting 2D SiN Monolayer

Contact Info

Product

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Single-layer metal halides MX₂ (X = Cl, Br, I): stability and tunable magnetism from first principles and Monte Carlo simulations