Journal of Contemporary Physics (Armenian Academy of Sciences)最新文献

{"title":"Paramagnetism of Surface Ni Atoms in Ni@C Nanocomposites. “Anomalous” Magnetic Size Effects in Ultrasmall Ni Particles: Manifestations of Surface Magnetic Anisotropy in Squid Magnetometry and FMR Spectra","authors":"E. G. Sharoyan,&nbsp;H. T. Gyulasaryan,&nbsp;A. S. Manukyan","doi":"10.1134/S1068337223030155","DOIUrl":"10.1134/S1068337223030155","url":null,"abstract":"<p>The dimensional magnetic effects of single-domain Ni nanoparticles encapsulated by a carbon shell (Ni@C nanocomposites) have been studied. The studied samples were obtained by solid-phase pyrolysis of solid solutions of nickel phthalocyanine (NiPc) and metal-free phthalocyanine (H₂Pc): (NiPc)_<i>x</i>(H₂Pc)_{1 – <i>x</i>}, where 0 ⩽ <i>x</i> ⩽ 1. The Ni concentration in the carbon matrix varied in the range of 0–12 wt %, the sizes of the average diameter of nanoparticles in different samples were from 4 to 40 nm. The paramagnetism of the surface and near-surface atoms of Ni nanoparticles, which is due to the charge transfer from the carbon matrix with the formation of Ni ions has been studied in detail. A method for determining the blocking temperature of superparamagnets in temperature measurements of the paramagnetic susceptibility in the case of high magnetic fields is considered. The magnetic characteristics, which reflect size effects in SQUID magnetometry and FMR, exhibit “anomalous” deviations in the range of ultrasmall particles. These are high values of the blocking temperature, high values of the coercive force, and the ferromagnetic resonance linewidth, as well as a significant shift of the effective g-factor in the FMR spectra. Generalizing equations are presented that include the contributions of the surface magnetic anisotropy along with the bulk magnetocrystalline anisotropy, which is consistent with the experimental results over the entire investigated range from 4  to 40 nm. It is shown that the parameters of the total magnetic resonance spectra (FMR + ESR) are caused by the ferromagnetism of the core of nickel nanoparticles and the paramagnetism of surface and near-surface Ni ions, as well as π-electrons of the organic matrix. A general diagram of the dependence of the coercive force on particle sizes for temperatures lower than the blocking temperature (<i>T</i> &lt; <i>T</i>_b) is also presented.</p>","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"58 3","pages":"287 - 298"},"PeriodicalIF":0.5,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preparation of the Ferromagnetic Intermetallic Compound Ni3Fe by Solution Combustion Synthesis","authors":"N. H. Amirkhanyan,&nbsp;Y. G. Grigoryan,&nbsp;M. K. Zakaryan,&nbsp;A. S. Kharatyan,&nbsp;H. T. Gyulasaryan,&nbsp;A. B. Harutyunyan","doi":"10.1134/S1068337223030040","DOIUrl":"10.1134/S1068337223030040","url":null,"abstract":"<p>The intermetallic compound Ni₃Fe was obtained using the solution combustion synthesis (SCS) method, based on heating an aqueous solution containing nitrates of the corresponding metals and hexamethylenetetramine (HMTA) in a nitrogen atmosphere. The limits for the implementation of a self-propagating reaction in the metal nitrates-HMTA system were determined depending on the amount of HMTA in the reacting mixture (<i>n</i>). It has been established that by changing the value of <i>n</i> it is possible to control phase composition and microstructure of the obtained SCS products. The X-ray examinations have shown that at <i>n</i> = 6, a single-phase target product Ni₃Fe is obtained, and electron microscopic studies indicated that the product is characterized by a pronounced porous structure because of abundant gas evolution during the SCS process. Based on thermogravimetric analyses of the individual compounds and the mixture of reagents (iron and nickel nitrates with HMTA), a possible mechanism for forming the target Ni₃Fe intermetallic compound is discussed. The magnetic characteristics of the synthesized substance have been studied.</p>","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"58 3","pages":"299 - 304"},"PeriodicalIF":0.5,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electromagnetic Vector Monochromatic Diffraction Fields and Fields of Charges in Media","authors":"M. K. Balyan","doi":"10.1134/S1068337223030076","DOIUrl":"10.1134/S1068337223030076","url":null,"abstract":"<p>Monochromatic electromagnetic fields are considered inside an arbitrarily chosen volume both in homogeneous and inhomogeneous media. Formulas for the fields in the selected volume are obtained using the vector Green’s function of the medium. Two forms of the vector Green’s function are found for homogeneous media. The Kirchhoff and Kirchhoff–Kottler vector formulas for the problem of diffraction by an aperture in an opaque screen are obtained. Because of the use of the vector Green’s function, the Kirchhoff–Kottler formula is obtained directly, without using additional assumptions.</p>","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"58 3","pages":"251 - 256"},"PeriodicalIF":0.5,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Signal-to-Noise Ratio of a Thermoelectric Single-Photon Detector with Different Values of the Physical Parameters of the Sensor Material","authors":"A. A. Kuzanyan,&nbsp;V. R. Nikoghosyan,&nbsp;A. S. Kuzanyan,&nbsp;S. R. Harutyunyan","doi":"10.1134/S106833722303012X","DOIUrl":"10.1134/S106833722303012X","url":null,"abstract":"<p>The processes of heat propagation in a three-layered detection pixel of a thermoelectric single-photon detector, consisting of an absorber (W), a thermoelectric sensor (La_0.99Ce_0.01B₆), and a heat sink (W) were studied using computer simulation. The absorption of UV photons with an energy of 7.1–124 eV has been studied. The simulation was based on the heat propagation equation from a limited volume. The temporal dependencies of the signal generated on the sensor were examined, and its power was determined. The equivalent power of Johnson and thermal noise was calculated. The signal-to-noise ratio was determined using different values of heat capacity, thermal conductivity, and the Seebeck coefficient of the sensor material. It was shown that the signal-to-noise ratio can be significantly greater than one. The obtained results reveal the prospects of using thermoelectric single-photon detectors as components of photonic integrated circuit.</p>","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"58 3","pages":"305 - 313"},"PeriodicalIF":0.5,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Generation of Radiation on Forbidden Transitions in the Laboratory Acoustic Plasma","authors":"A. S. Abrahamyan,&nbsp;A. H. Mkrtchyan,&nbsp;R. Yu. Chilingaryan","doi":"10.1134/S1068337223030027","DOIUrl":"10.1134/S1068337223030027","url":null,"abstract":"<p>Experimentally, under laboratory conditions in the nitrogen acoustic plasma in the region of the forbidden lines at 654.81 and 658.36 nm, a spectral emission line of high intensity was obtained (up to 17 stronger than the neighboring lines of the first positive system of nitrogen). The results were obtained both in pure low-pressure nitrogen acoustic plasma (several hundreds of Pa) and various mixtures containing nitrogen, including the CO₂ : N₂ : He = 1 : 1 : 8 mixture. The results obtained are explained by the acoustic plasma state of the discharge and an analog of Rahman scattering, which remove some of the quantum mechanical prohibitions. The possible influence of the Coriolis force is also considered.</p>","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"58 3","pages":"220 - 223"},"PeriodicalIF":0.5,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S1068337223030027.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the Role of Scalar Fields in the Evolutionary Development of the Early Universe","authors":"H. K. Teryan","doi":"10.54503/18291171-2023.16.2-66","DOIUrl":"https://doi.org/10.54503/18291171-2023.16.2-66","url":null,"abstract":"In most constructions of the inflationary regime of the development of the Universe, the \u0000presence of a specific scalar field (inflaton) is assumed, which contributes to the expansion of space \u0000at an enormous pace. In the present work, we study the dynamics of a conformally bound scalar \u0000field for the de Sitter case, in the presence of a closer connection between the potential and the space \u0000curvature R.","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"40 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79114708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Generic Technique for Explicit Definition of Models with SPT Phases","authors":"H. Topchyan","doi":"10.54503/18291171-2023.16.2-72","DOIUrl":"https://doi.org/10.54503/18291171-2023.16.2-72","url":null,"abstract":"","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"37 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90507265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Description of the Classical Diffraction Experiment of a Systemof Many Slits and the Interference Pattern of Two Sources within the Framework of a Single Scheme","authors":"A. Khachatrian, Zh. R. Panosyan, A. F. Parsamyan, L.R. Soghomonyan","doi":"10.54503/18291171-2023.16.2-40","DOIUrl":"https://doi.org/10.54503/18291171-2023.16.2-40","url":null,"abstract":"The problem of an approximate description of the wave field of many sources is \u0000considered. It is shown that, if the problem is considered more comprehensively, the description of \u0000the interference and diffraction experiments can be given within the framework of a single scheme. \u0000It is shown that the character of wave amplification in these two classical experiments is different. \u0000In the case of an interference experiment, the field amplification is fixed at a point, while in the case \u0000of a diffraction experiment the field amplification is fixed in the observation direction. The problem \u0000of determining the intensity maximum of a diffraction grating in the Fresnel pattern is studied under \u0000the condition that the maximum is satisfied in the Fraunhofer pattern. A condition under which a \u0000diffraction grating behaves like a lens is obtained.","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"129 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86381375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Effect of Modulated Millimeter Electromagnetic Waves of Non-Thermal Intensity on the Physical Properties of Aqueous Solutions","authors":"V. Kalantaryan, L. R. Sogomonyan, R. S. Ghazaryan, Yura Babayan","doi":"10.54503/18291171-2023.16.2-62","DOIUrl":"https://doi.org/10.54503/18291171-2023.16.2-62","url":null,"abstract":"The surface tension and density of bi-distilled water, water salt solution and salt \u0000solutions of the DNA, irradiated by non-thermal millimeter electromagnetic waves with the \u0000frequencies 64.5 GHz, 50.3 GHz and 48.3 GHz with modulation 1 Hz and 16 Hz are investigated. \u0000The measurements of test samples show that due to irradiation the surface tension does not \u0000change. The densities of water salt solution and the salt solutions of the DNA increase under \u0000irradiation at the frequencies 64.5 GHz and 50.3 GHz with modulation 1 Hz. When modulated \u0000with a frequency of 16 Hz, the density increases at a carrier frequency of 64.5 GHz and decreases \u0000at a carrier frequency of 50.3 GHz which coincides with the resonant frequencies of oscillations of \u0000water hexagonal structures.","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"34 14","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72492761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Functionalization of Graphene Oxide Layers Simultaneously with Liquid Phase Exfoliation","authors":"L. Anjo, A. Arshakyan, N. Gasparyan, A. A. Shahinyan, E. Aleksanyan, N. Margaryan","doi":"10.54503/18291171-2023.16.2-56","DOIUrl":"https://doi.org/10.54503/18291171-2023.16.2-56","url":null,"abstract":"Graphene oxide (GO) has garnered significant interest for its exceptional properties and potential applications in various fields. This study investigated the disparities between graphene oxide synthesized in an ammonia-acetone solution and graphene oxide synthesized in acetone using the exfoliation method. Raman spectroscopy, FTIR spectroscopy, and current-voltage characteristics analysis were employed to evaluate the samples. Raman spectroscopy analysis revealed distinct differences in the molecular composition and structural characteristics of the samples, as indicated by variations in the \"D,\" \"G,\" and \"2D\" peaks. FTIR spectroscopy identified various functional groups in both samples, with changes attributed to the presence of ammonium in one sample. Furthermore, the current-voltage characteristics analysis was conducted to assess the electrical properties of the graphene films. Results of the current-voltage characteristics analysis showed that the conductivity of the membranes obtained in an acetone medium was approximately an order of magnitude higher than that of the membranes obtained in an ammonia medium. This discrepancy suggests that the exfoliation in an acetone medium resulted in stronger doping of the graphene layers compared to the exfoliation in an ammonia solution. The linearity observed in the current-voltage characteristics can be attributed to the presence of a significant number of free electrons in the conduction band of the samples due to doping. These findings provide valuable insights into the structural, compositional, and electrical properties of graphene oxide synthesized using different methods and precursor solutions. Understanding these disparities is crucial for tailoring graphene-based materials to specific applications.","PeriodicalId":623,"journal":{"name":"Journal of Contemporary Physics (Armenian Academy of Sciences)","volume":"75 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83169438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}