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By conducting first-principles calculations with van der Waals correction, we investigate the structural, electronic, and magnetic properties of Gr/MnF3(4)/Gr sandwiched structures. ...The calculated binding energies were within 54–79meV per carbon atom for the four Gr/MnF3(4)/Gr sandwiched structures tested in our study. This result implies that the MnF3(4) clusters stabilize the AA and AB stacking in the Gr/MnF3(4)/Gr sandwich structures because of the high electronegativity of the clusters. Charge transfer from bilayer graphene to the MnF3(4) clusters is noted to induce effective hole doping in graphene. Spin polarization in the graphene layer is approximately 100% along the majority direction on the position of the Fermi level in the MnF3-doped structures. The band gaps of the spin-up and spin-down branches and the magnetic moments of the C atoms are increased by compression interlayer spacing. The MnF3 clusters affect the electronic and magnetic properties of graphene in the vicinity of the Fermi level; thus, the clusters are highly suitable for use as a dopant in spintronic applications.
Primordial Black Holes (PBH) arise naturally from high peaks in the curvature power spectrum of near-inflection-point single-field inflation, and could constitute today the dominant component of the ...dark matter in the universe. In this letter we explore the possibility that a broad spectrum of PBH is formed in models of Critical Higgs Inflation (CHI), where the near-inflection point is related to the critical value of the RGE running of both the Higgs self-coupling λ(μ) and its non-minimal coupling to gravity ξ(μ). We show that, for a wide range of model parameters, a half-domed-shaped peak in the matter spectrum arises at sufficiently small scales that it passes all the constraints from large scale structure observations. The predicted cosmic microwave background spectrum at large scales is in agreement with Planck 2015 data, and has a relatively large tensor-to-scalar ratio that may soon be detected by B-mode polarization experiments. Moreover, the wide peak in the power spectrum gives an approximately lognormal PBH distribution in the range of masses 0.01–100M⊙, which could explain the LIGO merger events, while passing all present PBH observational constraints. The stochastic background of gravitational waves coming from the unresolved black-hole-binary mergers could also be detected by LISA or PTA. Furthermore, the parameters of the CHI model are consistent, within 2σ, with the measured Higgs parameters at the LHC and their running. Future measurements of the PBH mass spectrum could allow us to obtain complementary information about the Higgs couplings at energies well above the EW scale, and thus constrain new physics beyond the Standard Model.
The magnetotransport properties of spin valve structure are highly influenced by the type of intervening layer inserted between the ferromagnetic electrodes. In this scenario, spin filtering effect ...at the interfaces plays a crucial role in determining the magnetoresistance (MR) of such magnetic structures, which can be enhanced by using a suitable intervening layer. Here, the authors investigate the spin filtering effect of the two‐dimensional layers such as hexagonal boron nitride (hBN), graphene (Gr), and Gr‐hBN hybrid system for modifying the magnetotransport characteristics of the vertical spin valve architectures (Ni/hBN/Ni, Ni/Gr/Ni, and Ni/Gr‐hBN/Ni). Compared to graphene, hBN incorporated magnetic junction reveals higher MR and spin polarizations (P) suggesting better spin filtering at the interfaces. The MR for hBN incorporated junction is calculated to be ≈0.83%, while that of graphene junction it is estimated to be ≈0.16%. Similar contrast is observed in the ‘P’ of ferromagnets (FMs) for the two junctions, that is, ≈6.4% for hBN based magnetic junction and ≈2.8% for graphene device. However, for Gr‐hBN device, the signal not only get inverts, but it also suggests efficient spin filtering mechanism at the FM interfaces. Their results can be useful to comprehend the origin of spin filtering and the choice of non‐magnetic spacer for magnetotransport characteristics.
The authors investigate spin filtering mechanism by incorporating 2D materials in spin valve devices. Comparing to graphene, hBN device reveals pronounced spintronic features suggesting better spin filtering at the interfaces. Furthermore, graphene and hBN incorporated magnetic junctions reveal positive MR, while that for Gr‐hBN heterostructure the signal not only becomes negative, but also facilitates efficient spin filtering at the interfaces.
The nanotwin structure and graphene (Gr)-reinforced phase can significantly enhance the mechanical properties of the material. However, there have been relatively few studies on the mechanisms ...underlying the strengthening resulting from the interaction between these two components in titanium–aluminum (TiAl) alloy materials. Here, molecular dynamics (MD) simulations were employed to investigate the mechanical properties and microstructural evolution of nanotwinned TiAl/Gr (nt-TiAl/Gr) composites under uniaxial loading. The study investigated the influence of Gr layer number and temperature on composite properties. Results demonstrate that the twin boundary structure interacts with graphene, enhancing mechanical properties synergistically. Relative to pure nt-TiAl, the maximum tensile strength increased by 7.42%, 24.66%, and 35.86% for varying Gr layers. Furthermore, the mechanical properties of nt-TiAl/Gr composites exhibit an inverse correlation with temperature, where maximum tensile strength decreases with temperature elevation. The synergy between Gr and the twin structure significantly inhibits dislocation diffusion and diminishes dislocation nucleation, thus improving the properties of the composite.
•The synergistic effect of twin boundary and graphene significantly enhanced the properties of TiAl alloy composites.•Both the twin boundary and graphene affect the formation and propagation of dislocations.•The increase of the tensile load activates the dislocation emission and forms a large number of entangled dislocation nodes.•The mechanical properties of nt-TiAl/Gr are significantly affected by the change of temperature.
Engineering high mass electroactive materials into hydrogel scaffolds remains an enormous challenge in achieving flexible energy storage devices. Herein, carboxymethyl cellulose (CMC) assisted high ...mass polyaniline (PANI) into an interpenetrating double-network polyethyleneimine/polyacrylamide (PEI/PAAM) hydrogel was developed. With the optimum mass loading of PANI at 9.04 mg/cm2, the all-in-gel CMC-PANI0.8M/PEI/PAAM supercapacitor can deliver a high specific capacitance of 679 mF/cm2, a maximum energy density of 58.82 μWh/cm2 at a power density of 14.69 mW/cm2, and an enhanced capacitance retention of 98 % after 5000 cycles. Such device can withstand severely bending/compressing deformations and operate properly at extreme temperatures (−30–70 °C). The CMC-PANI0.8M/PEI/PAAM hydrogel exhibits high sensitivity and stable electrical performance for wearable strain sensors. By connecting the supercapacitor with the strain sensor, the fabricated self-powered sensing system is capable of monitoring human activities accurately. Therefore, the multifunctional performance of the CMC-PANI0.8M/PEI/PAAM hydrogel is competent in the field of flexible electronics.
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