Physics of the Solid State最新文献

Iron–nickel alloys have received substantial interest because of their exceptional properties and diverse applications in technology and industry. In order to investigate their possible applications, the current research explored the structural, electronic, magnetic, and thermodynamic characteristics of tetrataenite L({{1}_{0}})-FeNi alloy through a first-principles approach. The computations were carried out utilizing the density functional theory’s full-potential linearized augmented plane wave. For the electronic exchange-correlation function, we employed the generalized gradient approximation (GGA) and GGA+U (Hubbard potential). The computed lattice parameter and bulk moduli for tetrataenite L({{1}_{0}})-FeNi exhibit excellent accord with previously reported data. The formation energy was calculated to be –0.18 eV/f.u. which confirming the structural stability of tetrataenite. The electronic structure revealed that the 3d orbitals of Ni and Fe are major elemental states that contribute to the metallic characteristics of the body-centered tetragonal (bct) L({{1}_{0}})-FeNi. Meanwhile, the thermodynamic characters are investigated using the quasi-harmonic Debye mode. The thermal expansion coefficient and the heat capacities are affected simultaneously by the pressure and temperature.

Raman scattering experiments were performed on barium carbonate at ambient temperature and high pressure within a hydrostatic environment, employing liquid nitrogen as the pressure-transmitting medium. This approach allowed for the investigation of hydrostatic pressure effects on the barium carbonate structure. Previous studies suggest that the stability threshold of the orthorhombic barium carbonate structure lies around 8 GPa. At pressures ranging from 8 to 10 GPa, the material exhibited a mixed phase. Upon reaching 10 GPa, the orthorhombic structure of barium carbonate vanished, giving way to a transformation into the trigonal phase. The phase transition significantly impacted the intensity of the Raman spectra, in-dicating an influence on the electronic structure, notably causing the electron cloud to rearrange and the bond character to alter. The re-emergence of the orthorhombic phase at a reduced pressure of 5.3 GPa und-erscored the pronounced hysteresis phenomena associated with the phase transition of barium carbonate. We determined that, while this phase transition is reversible upon pressure release, it is accompanied by persistent characteristic peaks of the trigonal phase, suggesting incomplete transformation back to the orthorhombic phase during decompression, with the residual proportion of the trigonal phase constituting approximately 12%.

X-ray absorption fine structure (XAFS) has been studied at the K-edge of copper in copper(II) complexes: Cu(L¹)₂Cl₂·2H₂O (1), Cu(L²)₂SO₄·5H₂O (2), Cu(L³)₂SO₄·5H₂O (3) and Cu(L⁴)₂SO₄·5H₂O (4), where L¹ = salicylaldehyde benzoyl hydrazine (SBH), L² = 5-nitro SBH, L³ = 5-methyl SBH, and L⁴ = 5‑bromo SBH. Cu K-Edge EXAFS beamline (BL-09) at 2.5 GeV established at Indus-2, RRCAT, Indore, India, was used to describe the data. Using the published crystal structures of each of these complexes, theoretical models have been created individually. Coordination numbers and bond length are among the characteristics of the structural that have been identified by fitting these theoretical models to the corresponding experimental EXAFS data. The first peak’s position in the Fourier transform, as well as the graphical technique of Levy, Lytle, and L.S.S., provide the value of the first shell bond length. The bond lengths of the complexes in study have been experimentally determined using the Levy, Lytle, and L.S.S. approach. These approaches’ outcomes have been compared to those of a theoretical approach.

Spinel oxides received widespread research interest because of versatility involved in various properties which are tunable as per disparity in composition, morphology, defects, doping sites, structure, lattice dynamics, interactions, surface area, substrate and so on. Due to the significant multifunctional applications, it is vital to probe these materials as they allow various dopants for the construction of diverse composites with novel and innovative performance. The present review is meant for the quicker understanding of 4-2 spinel oxides. The article covers the background of spinel oxides with their synthesis and applications. To begin with, spinel oxide crystal structure is introduced. It is observed that the diverse properties arise from the variety of cations substituted at the tetrahedral A-site and octahedral B-site. Traditional synthesis and novel methods for preparing spinel oxides is discussed in depth. Finally, it sheds light on recent advancement of spinel oxides for the multifunctional applications such as batteries, sensors, photocatalysts, multiferroics, memory devices, fuel cells and many more.

Noble metal nanoparticles (NMNPs), such as gold and silver, have been studied extensively in various fields in science and technology due to their peculiar properties, including high stability, easy chemical synthesis, tuneable surface functionalization and plasmonic property. Researchers have used them to fabricate biosensors. Indeed, biosensors have received a lot of attention because they enable the production of small, portable devices. The biosensor industry has grown; design attempts to improve and strengthen their detection characteristics and reduce their volumes. Enzymes are generally used to provide high selectivity and sensitivity; however, their short shelf life becomes a major drawback. Scientists have tried to find other materials to replace enzymes; having long-term stability and suitability for biosensors. Nanoparticles and metal oxides substituting enzymes in sensing devices represent the best candidate to achieve high selectivity and sensitivity. Herein, coated noble metal nanoparticles of various shapes and sizes, including nanospheres, nanowires, nanocubes and nanocylinders, are dispersed in surrounding media with different refractive indices to study, via the discrete dipole approximation (DDA) method, the response of their surface plasmon peaks. For this, a simulation model is proposed for the calculations of the plasmonic properties of the considered NPs, and analytical formulas are presented. The refractive index sensitivities (RISs) have been found to depend on the shape, size, core material, shell thickness and shell composition of the nanoparticles. LSPR sensors based on gold nanoparticles (AuNPs) exhibit the lowest RISs compared to the Ag and Al based nanosensors with a value of 93.33 nm/RIU (Ag) > 46 nm/RIU (Al) > 26 nm/RIU (Au), X = 5 nm. Numerical data clearly explain why silver is the plasmon material of choice for sensing applications.

Luminescence in Na₅Y(WO₄)₄:Nd³⁺ is investigated for the first time. The emission is in the near-infrared region. The well known ⁴F_3/2 → ⁴I_9/2 transition leads to most intense line at 1069 nm. The excitation and emission spectra are interpreted using the energy level diagram of Nd³⁺. The excitation spectrum is made up of a large number of sharp lines attributable to various f–f transitions. A weak band at 360 nm in the ex-citation spectrum is assigned to the host. Notwithstanding large Y–Y distances, the luminescence is quenched at concentrations exceeding 2 mol %. The critical distance for energy transfer among Nd³⁺ ions is found to be 32.85 Å.

In the current study, the density of state, condensation energy, specific heat, and magnetization in a spin triplet superconductor UTe₂ have been theoretically investigated. By utilizing the retarded double-time temperature-dependent Green’s function formalism and constructing a model Hamiltonian for the system, we derived expressions for the aforementioned parameters. MATLAB scripts were used to plot the phase diagrams. From the phase diagrams, we observed that the density of state of superconducting electron increases with excitation energy, reaching a maximum at the superconducting gap. Beyond this point, it decreases until it equals the normal state density. Condensation energy decreases with temperature, reaching a minimum at the superconducting transition temperature (T_C). However, it increases with T_C and eventually becomes zero, indicating that the superconducting and normal state energies are equal. Furhermore, specific heat increases with temperature, exhibiting a maximum at T_C followed by a jump, characteristic of a second-order phase transition from the superconducting to the normal state. Both itinerant and localized electron magnetization decrease with temperature, vanishing at T_C = 1.6 K and magnetic phase transition temperature T = 2 K, respectively, signifying a ferromagnetic to paramagnetic transition. Our findings align well with previous research.

At mesoscale, materials always exhibit a variety of novel properties that are completely different from those of bulk. In this work, the size (D) dependence functions of specific heat capacity C_p(D) and thermal expansion coefficient α(D) for metallic nanocrystals is built. The proposed model shows a good agreement as compared with the available experimental an simulation data of metal nanocrystals. Both C_p(D) and α(D) increase following the drop of D. In addition, it is found that the ratio of the solid/liquid interface energy γ_sl to surface stress f dominate the size dependence of C_p(D) and α(D), and this influence of γ_sl/f on C_p(D) and α(D) become greater as D decrease.

The electronic and magnetic properties of the doped Heusler alloys Rh₂Mn_1–xY_xGe and Rh₂Mn_1‒xY_xSn (x = 0, 0.25, 0.5, 0.75, 1) have been performed within the first-principles density functional theory (DFT) using the generalized gradient approximation (GGA) scheme, with the disordered structures. The calculated results reveal that with increasing Y content, the lattice parameter slightly increases except x = 0.5 for Rh₂Mn_1–xY_xSn. For both quaternary alloys it is found the local moments of Mn(Y) and Rh basically show a linear decreasing trend with increasing doping concentration and the total magnetic is negligible for x = 1. The minority-spin band component at the Fermi level for Rh₂Mn_1–xY_xGe and Rh₂Mn_1–xY_xSn decreases while the majority-spin band component at the Fermi is less affected with the substitution of Y atoms for Mn atoms.

Domain wall propagation and domain wall structure in spin dynamics play a crucial role in the development of new efficient memory devices. A transverse domain wall in the finite straight permalloy nanostrip has been investigated by applying the different normalized sinc current pulses and observing its motion. In addition, it has been observed that domain wall velocity gradually increases with the increase of the pulse period of the sinc pulse current. Furthermore, the pulse scale plays another crucial role in improving the domain wall velocity. Domain Wall velocity can be increased again by changing the non-adiabatic parameter. This study has successfully found the optimal values of the non-adiabatic parameter β and a scaler factor k that can be multiplied to pulse scale resulting in the highest domain wall velocity in particularly low current. It significantly established another control mechanism on the domain wall by varying the pulse scale and pulse period of the sinc pulse current. The present work shows that domain wall motion inside magnetic nano strips may be controlled with high efficiency and reliability using spin-polarized current pulse by solving the LLG equation and the object oriented micromagnetic framework (OOMMF) simulator. The development of racetrack memory technologies with enhanced data storing capacity will be significantly impacted by this study.