Current Applied Physics最新文献

The spin generation in strong spin-orbit coupling systems has led to a large spin-orbit torque. Recently, the orbital generation in weak spin-orbit coupling systems was reported. In this study, we investigate the spin-orbit torque of a nonmagnet/ferromagnet bilayer, where the nonmagnet is Pt, Mn, and Pt_0.5Mn_0.5 alloy, and the ferromagnet is Fe, Co, and Ni. The highest SOT efficiency, i.e., the spin Hall angle, of 0.32 was achieved with the Pt_0.5Mn_0.5/Ni structure, which is three times larger than 0.1 with the Pt/Ni structure. For the SOT mechanism, we discuss the enhanced orbital or spin generation in the PtMn alloy.

Vanadium-based kagomé systems AV₃Sb₅ (A = K, Rb, Cs) have emerged as paradigmatic examples exhibiting unconventional charge density waves (CDWs) and superconductivity linked to van Hove singularities (VHSs). Despite extensive studies, the three-dimensional (3D) nature of CDW states in these systems remains elusive. This study employs first-principles density functional theory and a tight-binding model to investigate the stacking-dependent electronic structures of 3D CDWs in AV₃Sb₅, emphasizing the significant role of interlayer coupling in behaviors of the VHSs associated with diverse 3D CDW orders. We develop a minimal 3D tight-binding model and present a detailed analysis of band structures and density of states for various 3D CDW stacking configurations, including those with and without a π-phase shift stacking of the inverse star of David, as well as alternating stacking of the inverse star of David and the star of David. We find that VHSs exist below the Fermi level even in 3D CDWs without π-phase shift stackings, and that these VHSs shift downward in the π-phase shift stacking CDW structure, stabilizing the $2\times 2\times 2$ π-shifted inverse star of David distortions in alternating vanadium layers as the ground state 3D CDW order of AV₃Sb₅. Our work provides the electronic origin of 3D CDW orders, paving the way for a deeper understanding of CDWs and superconductivity in AV₃Sb₅ kagomé metals.

We introduce experimental configurations of hyperspectral microscopy employing atomically thin materials as an example. The optical spectrum acquired from atomically thin materials contains rich information regarding their properties, enabling nondestructive characterization. Confocal measurement schemes have been widely used to investigate atomically thin materials, offering precise spectral data from a specific sample position. However, investigating the spatial variation of optical spectrum is necessary for a comprehensive characterization. One- or two-dimensional type hyperspectral imaging provides an effective approach to analyze the spatial distribution of spectral information. In this review paper, we explain the concepts of hyperspectral imaging with several examples applied to study of atomically thin materials.

CoS₂ thin films on PA 6 sheets were successfully formed by a two-step adsorption-diffusion method. A solution of pentathionate acid and a solution of Co(II) in complex form were used as a source for the formation of cobalt sulfide films. It has been established that increasing the duration of the first stage of the process, as well as increasing the temperature of the Co(II) precursor solution, plays a decisive role on the surface quality and positive physical properties of the resulting CoS₂ films. The surface morphology, physical properties and elemental composition of the obtained CoS₂ films have been investigated by means of XRD, SEM/EDS, ICP-OES and AFM. The formed CoS₂ thin films exhibit a broad absorption edge with a high absorption coefficient (α ≈ 10⁴ cm⁻¹). UV–Vis studies of films have revealed a significant influence of film formation conditions on the values of their optical band gap.

The present work is on the investigation of dielectric and ferroelectric properties of Ba_(0.70-x) Sm_xCa_0.30TiO₃; BSCT (x = 0.000, 0.005, 0.010, 0.015, 0.020 and 0.030) ceramics. The samples were prepared by the conventional solid-state reaction route method. The perovskite tetragonal structure was confirmed by X-ray diffraction analysis. The dielectric constant ‘ε’ and tangent loss ‘tanδ’ was measured over a temperature range (30 °C–150 °C) and frequency (100 Hz–100 kHz). All the samples show very small value of tanδ (<3 %) at 30 °C. The Curie temperature ‘T_c’ was found to decreases with increase the Sm-content. PE hysteresis loops were recorded at the different electric fields at 30 °C. The maximum value of electric field induced strain was observed for the sample with x = 0.015. The results show that the prepared samples are suitable for potential actuator and capacitor applications.

A series of Y₂O₃, Y₂O₃: Er³⁺ (1 %) and Y₂O₃-AG: Er³⁺ (1 %) (where AG = BO₃³⁻, PO₄³⁻, and SO₄²⁻) nanophosphors were prepared via a chemical combustion technique. The primary X-ray powder diffraction results showed that the Y₂O₃:Er³⁺ phosphor materials crystallized into a cubic standard structure, while the Y₂O₃-AG: Er³⁺ phosphor materials transformed to hexagonal and tetragonal structures for the [PO₄³⁻] and [BO₃³⁻]-based phosphors, respectively. However, no changes were observed for the [SO₄²⁻]-based phosphor materials. The scanning electron microscope micrographs revealed that the particles were formed in the nanometre range with different sizes and shapes. The fourier-transformed infrared spectra showed the presence of various structural groups in the pure Y₂O₃ and Y₂O₃-AG: Er³⁺ phosphors. In addition to that, the optical bandgap energy values were obtained using the diffuse reflection spectra (DRS) spectra and Kubelka-Munk function theory. Under UV-379 nm excitation for the Y₂O₃-AG: Er³⁺ phosphors, the Y₂O₃–SO₄: Er³⁺ emitted the most intense green light at 563 nm wavelength. The Commission Internationale de l'Elcairage colour coordinates and correlated color temperature values indicated that the Y₂O₃:Er³⁺, Y₂O₃-PO₄:Er³⁺, and Y₂O₃–SO₄:Er³⁺ phosphor materials are potential candidates for producing enhanced green color components in white light-emitting diode (w-LED) applications.

Hematite is a promising photoanode in photoelectrochemical water splitting system, but the slow water oxidation kinetics at the photoanode/electrolyte interface seriously limits the photoelectrochemical properties. Improving the surface state of hematite is an effective method to improve the transport and separation of carriers. Herein, we propose a strategy to recrystallize the hematite, which can effectively reduce the oxygen vacancies on the surface of hematite, increase active sites and improve the oxidation activity of water. The experimental results show that the charge recombination rate of the recrystallized Fe₂O₃ photoanode is reduced, and the carrier transport efficiency is improved. The photocurrent density at 1.23 V is four times higher than that of the original hematite, and the initial potential shifts negatively by about 20 mV, which is attributed to the upward bending of hematite energy band and the reduction of surface defects after treatment. This research provides a feasible strategy for designing efficient α-Fe₂O₃ photoanode.

We investigated the optical properties of 13 different dielectric materials (slide glass, quartz, Al₂O₃ (c-cut), DyScO₃ (110), KTaO₃ (001), LaAlO₃ (001), (LaAlO₃)_0.3-(Sr₂AlTaO₆)_0.7 (001) (LSAT), MgF₂ (100), MgO (100), SiC, SrTiO₃ (001), TbScO₃ (110), and TiO₂). The single-bounce reflectance spectra of the bulk samples were measured using Fourier transform infrared (FTIR) and monochromatic spectrometers across a wide spectral range, from far infrared to ultraviolet (80–50,000 cm⁻¹). Using the Kramers–Kronig analysis, we obtained the optical conductivity and dielectric function of the dielectric materials from their measured reflectance spectra. Moreover, we measured the transmittance spectra of the materials to obtain their bandgaps. We fitted the measured reflectance spectra using the Lorentz model to obtain phononic structures. Each dielectric material exhibits unique phononic structures and optical bandgaps, associated with the composition and crystal structure of the material. The observed optical properties of these dielectric materials provide valuable information for the optical analysis of thin films grown on them.

Sol-gel technique was used to develop M-type hexaferrites SrCo_xMg_xFe_12-2xO₁₉. The impact of doping of Co–Mg is analyzed on structural, dielectric, and electrical properties. The analysis was done in the frequency range of 150 Hz to 2 MHz. X-ray diffraction (XRD) analysis was performed for the determination of phase and structure of the prepared ferrites. The obtained results indicated the presence of an M-type hexagonal structure. The inclusion of Co–Mg caused a decrement in the crystallite size from 30.48 to 17.22 nm. The morphological analysis was performed using scanning electron microscopy (SEM), which reveals the formation of needle-shaped platelet structures. The doping had a non-monotonical effect on the dielectric constant and loss tangent. All the prepared compositions showed non-Debye-type relaxation for electric modulus. The increase in doping of Co–Mg caused a reduction in relaxation time. From the impedance spectroscopy, it was observed that both grains and grain boundaries affected the electrical characteristics.

Metal oxide nanoparticles, such as ZnO nanoparticles (NPs) and ITO NPs (indium tin oxide nanoparticles), were generated using the sol-gel and co-precipitation process to demonstrate photocatalytic degradation and antioxidant activities. The produced nanoparticles were examined for structural, morphological, and optical characteristics. ZnO and ITO NPs confirm their nanoscale properties by being smaller in size, ranging from 13 nm to 17 nm on average. The spherical nanoparticles were imaged using TEM, and the particle distribution was determined using a histogram plot. The optical property is a key criterion in determining nanomaterials' photocatalytic activity. UV–vis spectra confirm that the produced nanoparticles are a good candidate for photocatalytic activity. The study reports significant discoveries about the photocatalytic degradation and antioxidant properties of ZnO NPs and their composite with ITO NPs. Under light irradiation, ZnO-ITO NPs exhibit exceptional photocatalytic activity and strong antioxidant properties, effectively scavenging reactive oxygen species (ROS) and lowering oxidative stress. According to the findings, ZnO NPs and ZnO NPs-ITO NPs have enormous potential for photocatalytic degradation and antioxidant activities. The effectiveness of photocatalytic degradation of ZnO NPs and ZnO NPs-ITO NPs increases with pH from 4 to 8, with the highest efficiency seen at pH 8. Furthermore, their antioxidant properties make them attractive candidates for use in biomedical and pharmaceutical applications to treat oxidative stress-related diseases. More research and refining of these nanoparticles' properties are needed to fully realize their potential in these sectors.