Thermodynamic description of the Ising antiferromagnet on a triangular lattice with selective dilution by a modified pair-approximation method

Balcerzak, T.; Szałowski, K.; Jaščur, M.; Žukovič, M.; Bobák, A.; Borovský, M.

doi:10.1103/physreve.89.062140

Cited by 13 publications

(9 citation statements)

References 70 publications

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“…60 A highly inhomogeneous fluorine coverage was found to produce multilayer islands, folds, wrinkles, and ripples, all containing a lower content of fluorine, consequently forming a conductive superstructure through which the charge transport, mediated by itinerant π-electrons, occurred preferentially. 60 61,62 (see Methods Section below for details) indicated that the ferromagnetically ordered state was stable up to temperatures exceeding 300 K, in good agreement with the experimentally derived TC. The electronic structure displayed as density of states (DOS) of the C18(OH)4F6 model provided insights into the magnetic exchange mechanism in the G(OH)F system (see Figure 4b).…”

Section: Resultssupporting

confidence: 77%

Zigzag sp² Carbon Chains Passing through an sp³ Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

et al. 2018

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Stabilization of ferromagnetic ordering in graphene-based systems up to room temperature remains an important challenge owing to huge scope for applications in electronics, spintronics, biomedicine, and separation technologies. To date, several strategies have been proposed, including edge engineering, introduction of defects and dopants, and covalent functionalization. However, these techniques are usually hampered by limited temperature sustainability of ferromagnetic ordering. Here, we describe a method for the well-controlled sp 3 functionalization of graphene to synthesize zig-zag conjugated sp 2 carbon chains that can act as communication pathways among radical motifs. Zig-zag sp 2 /sp 3 patterns in the basal plane were clearly observed by high-resolution scanning transmission electron microscopy and provided a suitable matrix for stabilization of ferromagnetic ordering up to room temperature due to combined contributions of itinerant π-electrons and superexchange interactions. The results highlight the principal role of sp 2 /sp 3 ratio and super-organization of radical motifs in graphene for generating room temperature non-metallic magnets. KEYWORDS: hydroxofluorographene • fluorographene • magnetic carbon • hydroxyl • DFT calculations • density of states • 2D magnets • spintronicsGraphene, a two-dimensional (2D) layer of sp 2 -bonded carbon atoms arranged in hexagons, has attracted continuous attention of the scientific community over the past decade owing to its exceptional mechanical, electric, transport, and optical properties, which stem from its peculiar atomic organization and electronic structure. 1,2 It has been successfully tested in or proposed for a broad spectrum of applications 3 in various fields, such as electronics, 4 generation and storage of energy, 5,6 optics, 7 medicine, 8 printing technologies, 9 treatment of the environment, 10 and mechanical reinforcements. 11 However, despite its unique physical features, several drawbacks have been identified that hamper its use for specific processes and utilization. They include its high hydrophobicity, zero bandgap, and lack of magnetic response. In many cases, functionalization has been shown to be an effective strategy for overcoming these drawbacks. 12 For instance, it has been used to synthetize a number of graphene derivatives, such as graphene oxide, 13 graphane, 14 fluorographene 15,16 and other halogenated graphenes, 17 thiographene, 18 cyanographene, 19 graphene acid 19,20 and hydroxographene, 21 significantly extending the application potential of graphene-based materials and providing attractive/competitive alternatives in fields where pristine graphene fails.More than two decades ago, it was theoretically suggested that in a single layer of graphite, intrinsically diamagnetic, localized magnetic moments may emerge if an sp 3 -type defect is formed in the hexagonal carbon lattice. Since the first isolation of graphene in 2004, 1 the introduction of defects has become accepted as a promising way to endow graphene with magnetic proper...

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Section: Resultssupporting

confidence: 77%

Zigzag sp² Carbon Chains Passing through an sp³ Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

et al. 2018

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“…It should be noted from Ref. [30] that the specific heat displays no singular part but shows pronounced peaks corresponding to the Néel temperatures. This property is expressed as α = 0 for the AFIM in pair approximation and the scaling behaviour of R is, therefore, ∼ α−2 which is the same as α > 0.…”

Section: Thermodynamic Curvature Scalar For the Antiferromagnetic Isimentioning

confidence: 99%

“…Considering the magnetic Gibbs energy surface in the statistical Bethe (or pair) approximation and using the equilibrium conditions, they obtained two equations (also known as the Bethe equations) for the order parameters. In advanced years, the Bethe approximation (a useful tool for studying spin systems [25][26][27]) was also performed to calculate phase diagrams of AFIM in various lattice geometries [28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Antiferromagnetic Ising Model in the Framework of Riemannian Geometry

Erdem¹

2018

Acta Phys. Pol. B

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A metric is introduced on the three-dimensional space of two long-range sublattice order parameters and a short-range order parameter describing the Ising antiferromagnets in the Bethe approximation. The Riemannian geometry associated with this metric is investigated analytically. In terms of the equilibrium order parameters, thermodynamic curvature scalar (R) is derived and its temperature (T) dependence near the Néel transition temperature (T N) is analysed. A divergence to infinity is observed for the curvature on both sides of the Néel temperature (R → ∞) which can be scaled as R ∼ λ for T < T N , and R ∼ (−) λ for T > T N , with λ = λ = −2 and = 1 − T /T N. These observations fit well with those in the calculations of thermodynamic curvature in other spin models such as the spherical model and the ferromagnetic Ising model.

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“…However, their study involves only small system with sizes up to 30×30 and features no finite-size scaling analysis. Other studies analyzed the Kaya-Berker model using Monte Carlo (MC) simulations [21,22], effective-field theory (EFT) [23] and a modified pair-approximation (PA) method [24]. The EFT approach is based on a cluster approximation with clusters comprised of only a single spin and interactions with their nearest neighbors [25], which is quite similar to HSMF.…”

Section: Modelmentioning

confidence: 99%

Exact ground states of the Kaya-Berker model

Ohr

Hartmann

2018

Phys. Rev. E

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Here we study the two-dimensional Kaya-Berker model, with a site occupancy p of one sublattice, by using a polynomial-time exact ground-state algorithm. Thus, we were able to obtain T=0 results in exact equilibrium for rather large system sizes up to 777^{2} lattice sites. We obtained the sublattice magnetization and the corresponding Binder parameter. We found a critical point p_{c}=0.64(1) beyond which the sublattice magnetization vanishes. This is clearly smaller than previous results which were obtained by using nonexact approaches for much smaller systems. For each realization we also created minimum-energy domain walls from two ground-state calculations, for periodic and antiperiodic boundary conditions. The analysis of the mean and the variance of the domain-wall energy shows that there is no thermodynamic stable spin-glass phase at nonzero temperature, in contrast to previous claims about this model. For large values of p, the standard deviation of the domain-wall decreases with the system size like a power law with exponent roughly θ≃-0.1, which is different from the standard two-dimensional Ising spin glass where θ≃-0.29.

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Thermodynamic description of the Ising antiferromagnet on a triangular lattice with selective dilution by a modified pair-approximation method

Cited by 13 publications

References 70 publications

Zigzag sp² Carbon Chains Passing through an sp³ Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

Zigzag sp² Carbon Chains Passing through an sp³ Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

Antiferromagnetic Ising Model in the Framework of Riemannian Geometry

Exact ground states of the Kaya-Berker model

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Thermodynamic description of the Ising antiferromagnet on a triangular lattice with selective dilution by a modified pair-approximation method

Cited by 13 publications

References 70 publications

Zigzag sp2 Carbon Chains Passing through an sp3 Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

Zigzag sp2 Carbon Chains Passing through an sp3 Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

Antiferromagnetic Ising Model in the Framework of Riemannian Geometry

Exact ground states of the Kaya-Berker model

Contact Info

Product

Resources

About

Zigzag sp² Carbon Chains Passing through an sp³ Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene

Zigzag sp² Carbon Chains Passing through an sp³ Framework: A Driving Force toward Room-Temperature Ferromagnetic Graphene