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The spatial confinement of atoms at surfaces and interfaces significantly alters the lattice dynamics of thin films, heterostructures and multilayers. Ultrathin films with high dielectric constants (high-k) are of paramount interest for applications as gate layers in current and future integrated circuits. Here we report a lattice dynamics study of high-k Eu$_{2}$O$_{3}$ films with thicknesses of 21.3, 2.2, 1.3, and 0.8 nm deposited on YSZ(001). The Eu-partial phonon density of states (PDOS), obtained from nuclear inelastic scattering, exhibits broadening of the phonon peaks accompanied by up to a four-fold enhancement of the number of low-energy states compared to the ab initio calculated PDOS of a perfect Eu$_{2}$O$_{3}$ crystal. Our analysis demonstrates that while the former effect reflects the reduced phonon lifetimes observed in thin films due to scattering from lattice defects, the latter phenomenon arises from an ultrathin EuO layer formed between the thin Eu$_{2}$O$_{3}$ film and the YSZ(001) substrate. Thus, our work uncovers another potential source of vibrational anomalies in thin films and multilayers, which has to be cautiously considered.

Iron oxides are important materials for Geoscience but also for basic science and applied technologies (Kupenko et al., 2019). Iron monoxide is likely to be the final constituent of the evolution of subducted banded iron formations and might be a source of the low-velocity zones at the Earth’s core-mantle boundary (Dobson and Brodholt, 2005). The stability and high-pressure properties of FexO could, thus, determine the fate of banded iron formations and their potential role in processes in Earth and planetary interiors, including controls on redox cycles. FexO has the NaCl (B1) structure at ambient pressure and temperature and transforms into rhombohedral distorted-B1 phase (rB1) at about 16 GPa. A further transition from a rhombohedral rB1 phase to a hexagonal B8 phase has been proposed at 74 GPa and 900 K (Fei and Mao, 1994). Although numerous studies were focused on the investigation of the electronic and magnetic properties and phase diagram of FexO, information on the Fe2+/Fe3+ interplay, magnetic and structural coupling of FexO at high pressures and high temperature are very limited. We will present our investigation on the pressure dependence of the electronic, magnetic and structural properties of FexO by means of Synchrotron Mössbauer Source spectroscopy and Single-Crystal X-ray diffraction with diamond anvil cells up to 94 GPa and 1200 K. We will discuss the interplay between Fe2+ and Fe3+ and its effects on the electronic and magnetic properties of FexO and their potential role in the mineralogy, chemistry, and physics of the Earth’s deep interior.

Nature Communications 13(1), 7517 (2022). doi:10.1038/s41467-022-35110-x, Ferropericlase-magnesiowüstite (Mg,Fe)O is the second most abundant mineral in Earth’s lower mantle and the most common inclusion found in lower mantle diamonds. In pyrolitic mantle, it should theoretically contain < 20 mol% FeO. However, where the mineral is found as inclusions in diamond it shows a broad range of Mg# (Mg/(Mg+Fe)) between 12 and 93. Here we use synchrotron Mössbauer source spectroscopy (SMS), complemented by single-crystal X-ray diffraction to determine the structure and iron oxidation state of two magnesiowüstite and three ferropericlase inclusions in diamonds from São Luiz, Brazil. The Mg# of these inclusions varies between 16.1 and 84.5. All three ferropericlase inclusions are monomineralic and contain no ferric iron within the detection limit of SMS. Both magnesiowüstite inclusions show the presence of monocrystalline magnesioferrite (Mg,Fe)Fe$^{3+}$$_2$O$_4$) with an estimated 47-53 wt% of Fe$_2$O$_3$. We argue that the wide range of Fe concentrations observed in (Mg,Fe)O inclusions in diamonds and the appearance of magnesioferrite in Fe-rich inclusions result from oxidation of ferropericlase triggered by the introduction of subducted material into the lower mantle. Subducted carbonates react with Fe-metal to generate diamond and magnesiowüstite. Upon local metal exhaustion, the reaction continues with oxidation of magnesiowüstite into magnesioferrite, forming highly oxidised areas in the lower mantle., Published by Nature Publishing Group UK, [London]

В работе представлены актуальные проблемы современного менеджмента в России и даны рекомендации по повышению производительности труда, а также возвращению менеджменту важной роли в развитии экономики и увеличению благосостояния граждан.

We report the results of a search for a light pseudoscalar particle a that couples to electrons and decays to e+e− performed using the high-energy CERN SPS H4 electron beam. If such light pseudoscalar exists, it could explain the ATOMKI anomaly (an excess of e+e− pairs in the nuclear transitions of 8Be and 4He nuclei at the invariant mass ≃17 MeV observed by the experiment at the 5 MV Van de Graaff accelerator at ATOMKI, Hungary). We used the NA64 data collected in the “visible mode” configuration with a total statistics corresponding to 8.4×1010 electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter ε we also used the data collected in 2016-2018 in the “invisible mode” configuration of NA64 with a total statistics corresponding to 2.84×1011 EOT. The background and efficiency estimates for these two configurations were retained from our previous analyses searching for light vector bosons and axionlike particles (ALP) (the latter were assumed to couple predominantly to γ). In this work we recalculate the signal yields, which are different due to different cross section and lifetime of a pseudoscalar particle a, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space ma−ε in the mass range from 1 to 17.1 MeV is excluded. At the mass of the central value of the ATOMKI anomaly (the first result obtained on the beryllium nucleus, 16.7 MeV) the values of ε in the range 2.1×10−4

The current most stringent constraints for the existence of sub-GeV dark matter coupling to Standard Model via a massive vector boson A′ were set by the NA64 experiment for the mass region mA′≲250 MeV, by analyzing data from the interaction of 2.84×1011 100-GeV electrons with an active thick target and searching for missing-energy events. In this work, by including A′ production via secondary positron annihilation with atomic electrons, we extend these limits in the 200-300 MeV region by almost an order of magnitude, touching for the first time the dark matter relic density constrained parameter combinations. Our new results demonstrate the power of the resonant annihilation process in missing energy dark-matter searches, paving the road to future dedicated e+ beam efforts.