Search

Detecting unsafe levels of chemical gases and vapors is essential in improving and maintaining a healthy environment for all to enjoy. Propylene glycol is a colorless, synthetic gas commonly used in medications, fragrances, and cosmetics. It causes side effects such as headaches, lightheadedness, nausea, and fainting. So, monitoring of propylene glycol is critically vital. This study uses a defected photonic crystal as a propylene glycol THz sensor. Due to the high absorption of propylene glycol, the intensity of the resonant confined mode is very small. As a result, the performance of the designed sensor seems unsatisfactory. We will use parity-time symmetry for the first time in THz to magnify the resonant confined mode to detect propylene glycol. The effect of microcavity thickness, incident angle, and gain/loss factor will be studied. The optimized sensor recorded distinguished results compared to other studies for the detection of propylene glycol. [ABSTRACT FROM AUTHOR]

We have shown the feasibility of detecting gamma quanta in a neutron experiment in the mode of resonantly enhanced standing waves (RESW) from a 1 nm thick gadolinium film placed in a resonator structure consisting of a 50 nm niobium layer on a sapphire substrate and coated with a 10 nm tantalum-copper film alloy. The mass of gadolinium used in the experiment was 2 μg, which is 25 times less than that in the experiment by H. Zhang et al. (H. Zhang et al., Phys. Rev. Lett. 72, 3044 (1994)). Quantitative calculations show that the experimental conditions make it possible to detect a gamma signal at waveguide resonance from a gadolinium sample weighing 40 nanograms. Thus, RESW gamma spectrometry is a powerful method for characterizing heterostructures with ultrathin gadolinium layers. In particular, it can be used to study the kinetics of interaction of hydrogen with nanometer films in which a thin layer of gadolinium is used as a label layer. [ABSTRACT FROM AUTHOR]

Recently, optical simulation has attracted more attention in different thin film applications. Each layer's thickness and refractive index are the most essential simulation parameters. This paper discusses and fits the refractive index of aluminum nitride at different geometrical and physical conditions over a wide wavelength range for optical simulations. This study simplifies the use of aluminum nitride in thin film-simulated applications and devices. Plotted curves and fitted equations with MATLAB scripts for aluminum nitride refractive indices at different conditions will be provided to minimize modeling errors. [ABSTRACT FROM AUTHOR]

Polarized neutron reflectometry is an experimental method for studying metallic thin heterophase layered materials, polymer films, biological systems, the free surfaces of liquids, and magnetic fluids. It requires experimental equipment that includes a special magnetic system. The magnetic system described in this work, a vector magnet, will allow one to change the direction of the magnetic field in three directions, to place a temperature-control device inside at low and ultra-low temperatures, and will have an aperture that allows one to place a system for detecting neutrons and gamma rays outside. According to calculations, the cryomagnet will allow the application of a maximum field in the vertical plane of up to 3 T, and in the horizontal plane of up to 1 T. To manufacture a vector magnet, in this work, it is proposed to use a tape made of a high-temperature superconductor with a width of 4 mm. A cryostat with a vector magnet will be installed at the REMUR reflectometer on the eighth channel of the IBR-2 reactor. [ABSTRACT FROM AUTHOR]

The results of studying thin films and superlattices of rare-earth helimagnets Dy and Ho using a neutron reflectometer are presented. Neutron reflectometry is shown to allow the magnetic phase transitions in these nanostructures to be studied and information about the periodicity of magnetic helices in them to be collected. It is proposed to create a neutron reflectometer capable of conducting polarization analysis on the DARIA compact neutron source, optimized for studying long-period magnetic ordering in rare-earth helimagnets, and the possible directions of this optimization are indicated. [ABSTRACT FROM AUTHOR]

Binary and ternary multilayers comprising paramagnetic and ferromagnetic materials filter out a specific neutron wavelength from the reflected broad spectrum. The effect of the grazing angle, the magnetization of the ferromagnetic layers, and the scattering length density of the ferromagnetic layers for both structures are numerically studied. The best performance of the proposed filter, such as the broadest neutron bandgap of 0.46 Å and the smallest bandwidth of the transmitted beam of 0.0016 Å, was achieved using the binary structure at magnetization of 40 kOe. These findings hold potential in the nuclear fields, including neutron waveguides and filters. [ABSTRACT FROM AUTHOR]

The possibility of using the resonant scattering of neutrons by gadolinium atoms in the reflectometry of polarized neutrons to determine the interaction potential and calculate the structural and magnetic characteristics of multilayer metal films is considered. The experimental data of polarized-neutron reflectometry for Fe/Cr/Fe films with ferromagnetic and antiferromagnetic ordering of the Fe layers are presented. Using the modulus and phase of the reflection coefficient reconstructed for the studied part of the sample, the structural characteristics and types of magnetic ordering of the layers are determined. Processing is carried out jointly for two scattering channels. For each channel, the modulus and phase are analyzed simultaneously. [ABSTRACT FROM AUTHOR]

The results of studying a superlattice of alternating layers of rare-earth helimagnets [Dy(6 nm)/Ho (6 nm)] × 34 by neutron reflectometry and X-ray diffraction are presented. It is shown that during the growth of helimagnetic structures on sapphire substrates with a Nb buffer layer by magnetron sputtering, the orientational relations Al2O3||(110)Nb|| (Dy/Ho) and the crystal lattices of Nb and the structure of rare-earth helimagnets are completely relaxed. It is also found that two different magnetic helicoids are formed in the sample, propagating coherently in Dy and Ho layers, respectively, with periods and Néel and Curie temperatures that differ from the characteristic temperatures of single crystals and thin one-component Dy and Ho films. [ABSTRACT FROM AUTHOR]

Herein, we theoretically suggest one-dimensional photonic crystal composed of polymer doped with quantum dots and porous silicon. The present simulated design is proposed as a refractive index biosensor structure based on parity-time symmetry. Under the parity-time conditions, the transmittance of the resonant peaks is magnified to be 57,843% for refractive index 1.350, 2725% for 1.390, 2117% for 1.392, 1502% for 1.395, 1011% for 1.399, and 847% for 1.401. By magnification, we can distinguish between different refractive indices. The present design can record an efficiency twice the published designs as clear in the comparison table. Results clear that the sensitivities are 635 nm/RIU and 1,000,000%/RIU. So, it can be used for a broader range of detection purposes. [ABSTRACT FROM AUTHOR]

The role of size effects in the formation of the magnetic structure of Dy and Ho thin films in absence of epitaxial strain is studied in this work. It was found that, for Dy in the temperature range between the Néel temperature and the Curie temperature of bulk Dy and, for Ho, in the temperature range between the Néel temperature and the temperature of phase transition into the conic phase, the temperature dependences of the period of magnetic helicoid in the bulk and film metals are similar. The character of the transition into the ferromagnetic phase in the Dy films changes at lower temperatures, and the transition into the commensurable conic phase in the Ho films is suppressed. This is explained exclusively by the influence of dimensional effects. [ABSTRACT FROM AUTHOR]

The neutron reflectometry method is used to measure the spatial profile of the potential of interaction between neutrons and a medium. At the interface between media, the interaction potential is the sum of potentials of individual isotopes. Neutrons and gamma radiation emitted by the atomic nuclei of an element are recorded to determine the potential of interaction between neutrons and individual isotopes. Channels for the recording of gamma quanta and spin-flipped neutrons are created using a REMUR spectrometer. Channel testing results are given, model calculations of the neutron absorption coefficients are carried out, and prospects related to the recording of gamma quanta and polarized neutrons are discussed. [ABSTRACT FROM AUTHOR]

In this paper, the results of investigating thin films of rare-earth helimagnetics (REMs) Dy and Ho by polarized neutron reflectometry are presented. It is shown that the growth by magnetron sputtering of rare-earth structures on sapphire substrates with a buffer layer Nb Al2O3||[110]Nb|| leads to complete relaxation of the Nb crystal lattices and the rare-earth film. It is found that some magnetic phase transitions typical of bulk Dy and Ho are not observed in 200 nm [0001]R thin films or are observed in a modified form. Differences between the Néel and Curie temperatures of thin REM films compared to bulk REMs are determined based on polarized-neutron-reflectometry data and measurements of the temperature dependence of the magnetization in the sample plane. [ABSTRACT FROM AUTHOR]

Using high-vacuum magnetron sputtering, epitaxial Dy films were synthesized on Nb and Ta buffer layers on single-crystal Al2O3 substrates with different crystallographic orientations. It was established that the epitaxial relationships [11 0]Al2O3|| [011]Nb(Ta) and [1 02]Al2O3||[011]Nb(Ta) are satisfied with growing a Nb(Ta) buffer layer on single-crystal sapphire substrates with different crystallographic orientations. The second relationship has never been observed up to now; this may be because the growth rates upon magnetron sputtering are approximately two orders higher than those upon molecular-beam epitaxy. It was established that the Dy crystal lattice expansion in the basal plane by 2.8–3% occurs in all cases. Contrary to the samples grown on Nb, the Dy films grown on the Ta buffer layers are characterized by a larger value of the saturation magnetization, whereas its maximum value is attained in the polycrystalline Dy films. [ABSTRACT FROM AUTHOR]

The heterogeneous ferromagnetic–superconducting layered heterostructures V/Fe0.7V0.3/V/Fe0.7V0.3/Nb and Nb/Ni0.65(0.81)Cu0.35(0.19), which contain magnetic clusters and ferromagnetic domains, are studied. The magnetic and superconducting properties of the structures depend on the magnetic-layer thickness, the magnetic field, and the time elapsed from structure preparation. We detected the interaction of clusters with a domain structure, diamagnetism and magnetization reversal of the magnetic layer during the superconducting transition in a ferromagnetic–superconducting heterostructure, and a superconducting transition in the magnetic layer. The magnetic and resistive properties of the heterostructures changed in several weeks and months. [ABSTRACT FROM AUTHOR]

The heterogeneous ferromagnetic–superconducting layered heterostructures V/Fe0.7V0.3/V/Fe0.7V0.3/Nb and Nb/Ni0.65(0.81)Cu0.35(0.19), which contain magnetic clusters and ferromagnetic domains, are studied. The magnetic and superconducting properties of the structures depend on the magnetic-layer thickness, the magnetic field, and the time elapsed from structure preparation. We detected the interaction of clusters with a domain structure, diamagnetism and magnetization reversal of the magnetic layer during the superconducting transition in a ferromagnetic–superconducting heterostructure, and a superconducting transition in the magnetic layer. The magnetic and resistive properties of the heterostructures changed in several weeks and months. [ABSTRACT FROM AUTHOR]

An ionization chamber is installed to the REMUR neutron spectrometer, situated at channel no. 8 of the IBR-2. A layered structure containing a layer of the isotope under study with a thickness of several nanometers is placed into the chamber. A neutron beam enters the chamber and is incident on the structure. The reflected neutron beam and the neutron beam transmitted through the structure are recorded by a detector located outside the chamber. A fraction of neutrons incident on the structure is captured by the nuclei of the isotope under study. As a result, secondary radiation is generated in the form of charged particles, which are recorded by the ionization chamber. The dependences of the neutron and charged particle intensities on the transmitted wave vector of neutrons are used to determine the spatial dependences of the potential of interaction between neutrons with the entire structure and with a layer of the isotope under study. The neutron spectrometer in grazing geometry, using which the neutrons and charged particles are recorded in studying the layered structures, is described. The results of spectrometer testing with the use of structures containing the 6Li isotope are given. [ABSTRACT FROM AUTHOR]

Abstract: The angular divergence of a narrow divergent neutron microbeam escaping from the end of a three-layer film waveguide has been measured as a function of the waveguiding layer width and the neutron wavelength. This microbeam originates from a conventional neutron beam that is incident on the surface of the film, propagates along the middle layer, and escapes from the end face in the form of a narrow divergent microbeam. The experimental results are compared with calculations. [ABSTRACT FROM AUTHOR]

We have studied the Nb(70 nm)/Ni0.65Cu0.35(6.5 nm)/Si layered structure in the temperature range T = 1.5-10 K using polarized neutron reflectometry. The correlation of the states of magnetic structures is observed at temperature T = 9 K, which is slightly higher than the superconducting transition temperature Tc = 8.5 K of the structure. At temperature T = 4 K, which is lower than Tc, the effect of reflexivity of magnetic states existing at T = 9 K was observed. [ABSTRACT FROM AUTHOR]

Textured Al-doped ZnO films are studied using neutron reflectometry. The films are quasiperiodic structures with a period of several nanometers. The films are inhomogeneous in a surface layer with a thickness of 10-20 nm. [ABSTRACT FROM AUTHOR]

The propagation of neutrons in the middle layer of a planar waveguide in the form of a three-layer thin film has been investigated. The microbeam from the end face of the film has been registered. The neutron channeling length has been measured as a function of the thickness of the upper waveguide layer and the resonance order. The experimental data have been compared with theoretical results. [ABSTRACT FROM AUTHOR]

We have proposed a real-time method of neutron reflectometry. The magnetic state of the Ta/V/FM/Nb/Si ferromagnetic-superconducting system has been analyzed. Relaxation of the inhomogeneous magnetic state with a characteristic time of several hours, which depends on the magnetic field magnitude and temperature, has been observed. The relaxation of the domain structure has changed upon a transition of the V and Nb layers to the superconducting state. It has been concluded that real-time reflectometry data for polarized neutrons are important for determining the origin of magnetism in ferromagnetic-superconducting layered structures. [ABSTRACT FROM AUTHOR]

The influence of superconductivity on ferromagnetism in the layered Ta/V/FeV/V/FeV/Nb/Si structures consisting of ferromagnetic and superconducting layers is studied using polarized neutron reflection and scattering. It is experimentally shown that magnetic structures with linear sizes from 5 nm to 30 μm are formed in these layered structures at low temperatures. The magnetization of the magnetic structures is suppressed by superconductivity at temperatures below the superconducting transition temperatures in the V and Nb layers. The magnetic states of the structures are shown to undergo relaxation over a wide magnetic-field range, which is caused by changes in the states of clusters, domains, and Abrikosov vortices. [ABSTRACT FROM AUTHOR]

Examples of the application of a cryogenic moderator in the REMUR time-of-flight neutron reflectometer of the IBR-2 pulsed reactor (Dubna) are given. The results of two experiments are presented: spatial beam splitting upon reflection from a magnetically noncollinear film and the recording of a microbeam formed by a layered waveguide. A conclusion concerning the efficiency of the cryogenic moderator for experiments of this type is made. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X21880013 [ABSTRACT FROM AUTHOR]