The giant effect of magnetic ordering on a sound velocity in a sigma-Fe55Cr45 alloy

We studied atomic dynamics of sigma-Fe(100-x)Cr(x) (x=45 and 49.5) alloys using nuclear inelastic scattering of synchrotron radiation. For the sigma-Fe55Cr45 alloy, the derived reduced iron-partial density of phonon states reveal a huge difference in the low-energy region between magnetic and paramagnetic states. The latter implies a ca.36% increase of the sound velocity in the magnetic phase, which testifies to a magnetically-induced hardening of the lattice.Comment: 8 pages, 3 figures, 17 reference

A high spatial resolution synchrotron Mössbauer study of the Tazewell IIICD and Esquel pallasite meteorites.

Metallic phases in the Tazewell IIICD iron and Esquel pallasite meteorites were examined using 57Fe synchrotron Mössbauer spectroscopy. Spatial resolution of ~10-20 μm was achieved, together with high throughput, enabling individual spectra to be recorded in less than 1 h. Spectra were recorded every 5-10 μm, allowing phase fractions and hyperfine parameters to be traced along transects of key microstructural features. The main focus of the study was the transitional region between kamacite and plessite, known as the "cloudy zone." Results confirm the presence of tetrataenite and antitaenite in the cloudy zone as its only components. However, both phases were also found in plessite, indicating that antitaenite is not restricted exclusively to the cloudy zone, as previously thought. The confirmation of paramagnetic antitaenite as the matrix phase of the cloudy zone contrasts with recent observations of a ferromagnetic matrix phase using X-ray photoemission electron spectroscopy. Possible explanations for the different results seen using these techniques are proposed.The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007 - 2013) / ERC Grant Agreement No. 320750

Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation

Nuclear inelastic scattering (NIS) spectra were recorded for the spin-crossover complexes STP and ETP (STP = [Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg- ethane)](ClO4)2 and ETP = [Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg-butane)](ClO4)2) at 30 K and at room temperature and also at ambient pressure and applied pressure (up to 2.6 GPa). Spin transition from the high-spin (HS) to the low-spin (LS) state was observed by lowering temperature and also by applying pressure at room temperature and has been assigned to the hardening of iron-bond stretching modes due to the smaller volume in the LS isomer

Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure

The temperature and pressure dependence of the partial density of phonon states of iron atoms in superconducting Fe1.01Se was studied by 57Fe nuclear inelastic scattering (NIS). The high energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features towards higher energies by ~4% with decreasing temperature from 296 K to 10 K was found. However, no detectable change at the tetragonal - orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase of the superconducting temperature from 8 K to 34 K, results in an increase of the optical phonon mode energies at 296 K by ~12%, and an even more pronounced increase for the lowest-lying transversal acoustic mode. Despite these strong pressure-induced modifications of the phonon-DOS we conclude that the pronounced increase of Tc in Fe1.01Se with pressure cannot be described in the framework of classical electron-phonon coupling. This result suggests the importance of spin fluctuations to the observed superconductivity

Double-spiral magnetic structure of the Fe/Cr multilayer revealed by nuclear resonance scattering

We have studied the magnetization depth profiles in a [57Fe(dFe)/Cr(dCr)]x30 multilayer with ultrathin Fe layers and nominal thickness of the chromium spacers dCr 2.0 nm using nuclear resonance scattering of synchrotron radiation. The presence of a broad pure-magnetic half-order (1/2) Bragg reflection has been detected at zero external field. The joint fit of the reflectivity curves and Mossbauer spectra of reflectivity measured near the critical angle and at the "magnetic" peak reveals that the magnetic structure of the multilayer is formed by two spirals, one in the odd and another one in the even iron layers, with the opposite signs of rotation. The double-spiral structure starts from the surface with the almost antiferromagnetic alignment of the adjacent Fe layers. The rotation of the two spirals leads to nearly ferromagnetic alignment of the two magnetic subsystems at some depth, where the sudden turn of the magnetic vectors by ~180 deg (spin-flop) appears, and both spirals start to rotate in opposite directions. The observation of this unusual double-spiral magnetic structure suggests that the unique properties of giant magneto-resistance devices can be further tailored using ultrathin magnetic layers.Comment: 9 pages, 3 figure

ELECTROPHYSICAL PROPERTIES OF POROUS TANTAL PENTAXIDE FILMS

In the present work, studies of the effect of carbon on structure and electrical characteristics on the example of other oxide dielectrics used in integrated circuit technology are continued. The experiment was performed on metal-insulator-metal (MDM) structures. As a dielectric, films of tantalum pentoxide obtained by magnetron sputtering of the Ta: C composite target in an oxygen atmosphere were used

Dynamics of subjective student wellbeing during the COVID-19 pandemic

BACKGROUND: Because the COVID-19 pandemic has continued for a long time, it has become necessary to explore the dynamics of mental health phenomena during this period. AIM: To identify the dynamics of the emotional component of the subjective wellbeing of the personality of students in the psychological and pedagogical areas at various stages of the COVID-19 pandemic. MATERIAL AND METHODS: The study involved 911 students in the psychological and pedagogical areas at the University of Tyumen, Kurgan State University, and Ural Federal University. The research method used was the scale of subjective wellbeing by Perrudet-Badoux as adapted by M.V. Sokolova. Measurements were taken in April 2020, May 2021, October 2021, and January 2022. RESULTS: In April 2020, at the beginning of the pandemic, the university students had the lowest indicators of the emotional component of the subjective wellbeing of the individual. A year later, in May 2021, there was an increase in subjective wellbeing, which, however, was not statistically significant. The trend of improvement in subjective wellbeing continued for six months to October 2021, when it became significantly higher than when the pandemic began. At the fourth measurement in January 2022, subjective wellbeing had stabilized, indicating that the students had adapted to the conditions of the pandemic. CONCLUSION: The emotional component of the subjective wellbeing of the personality of students was subject to dynamics of the COVID-19 pandemic. During the two years of the pandemic, university students have adapted to the stressful situation of the pandemic as reflected by the improvement and stabilization of the emotional component of subjective wellbeing. © Eco-Vector, 2022.Russian Foundation for Basic Research, РФФИавторства международным критериям ICMJE (все авторы внесли существенный вклад в разработку концепции, проведение ис-следования и подготовку статьи, прочли и одобрили финальную версию перед публикацией). Наибольший вклад распределён следующим образом: И.В. Васильева — сбор и анализ данных, статистический анализ, интерпретация результатов, правки текста, подготовка первого варианта статьиМ.В. Чумаков — подготовка протокола исследования, сбор и анализ данных, их интерпретация, правки текста, подготовка обзора литературы, окончательная редакция статьи. Authors’ contribution. I.V. Vasilyeva collected and analyzed the data, performed statistical analysis and interpretation of results, edited the text, prepared the initial draft of the articleM.V. Chumakov prepared the study protocol, collected, analyzed, and interpreted the data, edited the text, prepared the literature review, prepared the final revision of the article. Thereby, all authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work. Финансирование. Исследование выполнено при финансовой поддержке Российского фонда фундаментальных исследований в рамках научного проекта № 20-413-720004 р_а_Тюменская об-ласть. Funding sources. The study was supported by the Russian Foundation for Basic Research within the scientific project N. 20-413-720004 r_a_Tyumenskaya oblast. Конфликт интересов. Авторы подтверждают отсутствие явных и потенциальных конфликтов интересов при написании данной статьи. Competing interests. The authors declare no conflict of interest. Благодарности. Авторский коллектив благодарит за помощь в сборе данных студентов Тюменского государственного универ-ситета, Курганского государственного университета, Уральского федерального университета имени первого Президента России Б.Н. Ельцина, которые в непростое время пандемии COVID-19 от-кликнулись на просьбу об участии в исследовании. Acknowledgements. The team of authors expresses gratitude to students of University of Tyumen, Kurgan State University, Ural Federal University named after the First President of Russia B.N. Yeltsin for assistance in data collection, who responded to a request to participate in the study during hard times of the COVID-19 pandemic

Tracking the connection between disorder and energy landscape in glasses using geologically hyperaged amber

Fossil amber offers the unique opportunity of investigating an amorphous material which has been exploring its energy landscape for more than 110 Myears of natural aging. By applying different x-ray scattering methods to amber before and after annealing the sample to erase its thermal history, we identify a link between the potential energy landscape and the structural and vibrational properties of glasses. We find that hyperaging induces a depletion of the vibrational density of states in the THz region, also ruling the sound dispersion and attenuation properties of the corresponding acoustic waves. Critically, this is accompanied by a densification with structural implications different in nature from that caused by hydrostatic compression. Our results, rationalized within the framework of fluctuating elasticity theory, reveal how upon approaching the bottom of the potential energy landscape (9% decrease in the fictive temperature $T_f$) the elastic matrix becomes increasingly less disordered (6%) and longer-range correlated (22%).Comment: 9 pages, 10 figure