Spectroscopy of high proper motion stars in the ground--based UV

Based on high quality spectral data (spectral resolution R>60000) within the wavelength range of 3550-5000 AA we determined main parameters (effective temperature, surface gravity, microturbulent velocity, and chemical element abundances including heavy metals from Sr to Dy) for 14 metal-deficient G-K stars with large proper motions. The stars we studied have a wide range of metallicity: [Fe/H]=-0.3 \div -2.9. Abundances of Mg, Al, Sr and Ba were calculated with non-LTE line-formation effects accounted for. Abundances both of the radioactive element Th and r-process element Eu were determined using synthetic spectrum calculations. We selected stars that belong to different galactic populations according to the kinematical criterion and parameters determined by us. We found that the studied stars with large proper motions refer to different components of the Galaxy: thin, thick disks and halo. The chemical composition of the star BD+80 245 located far from the galactic plane agrees with its belonging to the accreted halo. For the giant HD115444 we obtained [Fe/H]=-2.91, underabundance of Mn, overabundance of heavy metals from Ba to Dy, and, especially high excess of the r-process element Europium: [Eu/Fe]=+1.26. Contrary to its chemical composition typical for halo stars, HD115444 belongs to the disc population according to its kinematic parameters.Comment: 16 pages, 4 figures, 5 tables, "UV Universe-2010 (2nd NUVA Symposium) conference

High-intensity pulsed ion beam treatment of amorphous iron-based metal alloy

© 2020 Published under licence by IOP Publishing Ltd. The results of intense pulsed ion beam (IPIB) treatment of the soft magnetic amorphous alloy of a FINEMET-type are presented. Foil produced from the alloy was irradiated with short (about 100 ns) pulses of carbon ions and protons with energy of up to 300 keV and an energy density of up to 7 J/cm2. X-ray diffraction, Mössbauer spectroscopy and magnetic measurements were used to investigate structural and magnetic properties of irradiated foils. It is shown that the foil remains intact after the treatment, and the crystal structure still amorphous. Spontaneous magnetization vector is found to lie almost along perpendicular to the foil plane after irradiation, whereas for the initial amorphous foil it belongs to the plane. The magnetic properties of the foil undergo changes: the coercive force decreases, the saturation induction increases slightly, and the magnetization curve has shallower slope

Spin crossover properties of Fe(III) complexes in [Fe (bzacen)(tvp)]BPh<inf>4</inf>·nSolv chain structures: EPR study

© 2020 John Wiley & Sons, Ltd. Two types of Fe(III) polynuclear iron(III) 1D-chain coordination compounds of the general formula [Fe (L)(tvp)]BPh4 nSolv, where L = dianion of N,N′-ethylenebis (benzoylacetylacetone)2,2′-imine (bzacen), tvp = 1,2-di(4-pyridyl)ethylene were synthesized and studied by the electron paramagnetic resonance (EPR) and magnetic susceptibility methods in the temperature range (100–300) К. Two types of spin-variable complexes are formed depending on the time of precipitation of the complexes from the same solution leading to differently solvated species. They have different characteristics of the local ligand field and the spin transition behavior. The thermodynamic parameters of spin transitions were determined from the temperature dependence of the EPR signals integral intensity. The energy levels splitting values obtained by analyzing g-factors of low-spin Fe(III) centers evidenced not only on the crucial role of low-symmetry distortions on the principal possibility of spin-crossover processes, but also on the temperature peculiarities of spin transitions

OD ESR signals of excess electrons in liquid hydrocarbons depending on the geminate recombination parameters, theory and experiment

The intensity of optically detected ESR (OD ESR) signals from radical-ion pairs in solution under ionizing irradiation has been investigated experimentally and theoretically as a function of the microwave power, the geminate recombination parameters, the diffusion coefficient, the distance distribution function of pairs, and the spin-lattice relaxation time. In line with theoritical predictions, the temperature dependence of an OD ESR signal has been shown to have a maximum depending on the microwave power. The experimental dependence has been measured for the system e- + triethylamine+ (TEA) in 3-methylpentane. Agreement between the theoretical and experimental dependences is discussed. © 1985

OD ESR signals of excess electrons in liquid hydrocarbons depending on the geminate recombination parameters, theory and experiment

The intensity of optically detected ESR (OD ESR) signals from radical-ion pairs in solution under ionizing irradiation has been investigated experimentally and theoretically as a function of the microwave power, the geminate recombination parameters, the diffusion coefficient, the distance distribution function of pairs, and the spin-lattice relaxation time. In line with theoritical predictions, the temperature dependence of an OD ESR signal has been shown to have a maximum depending on the microwave power. The experimental dependence has been measured for the system e- + triethylamine+ (TEA) in 3-methylpentane. Agreement between the theoretical and experimental dependences is discussed. © 1985

Magnetic properties of ludwigite Mn<inf>2.25</inf>Co<inf>0.75</inf>BO<inf>5</inf>

Needle-shape single crystals of Mn2.25Co0.75BO5 ludwigite were synthesized by the flux technique and investigated by means of X-ray diffraction, static magnetic susceptibility and specific heat measurements. Magnetization and specific heat experiments showed the presence of ferrimagnetic ordering near TN≃61K. Below this temperature the magnetic properties demonstrated the angular dependence and the high magnetic hardness in a magnetic field applied perpendicular to the crystallographic c axis, which is similar to other cobalt-containing ludwigites. The effective magnetic moment per magnetic ion 4.8μB was calculated from the paramagnetic data. Analysis of the phonon contribution to the specific heat allowed to distinguish the magnetic contribution CM, which has two features. One of which was observed at TN and can be attributed to strong exchange interactions between spins of magnetic ions. The second one at T = 11.6 K is due to the effect of the ligands crystal field on a magnetic ion with S>1∕2

Structure Features of the Nanocrystalline Ni Films Formed by Ion Sputtering Technique

Abstract: Thin nanocrystalline Ni films with a thickness of ~340–360 nm are synthesized by ion sputtering on single crystal Si(111) substrates under high vacuum conditions. X-ray diffraction, scanning electron microscopy with microanalysis, vibration magnetometry and differential thermomagnetic analysis are used to study structure, magnetic phase composition, and magnetic properties of the initial and thermally annealed Ni films. It is found that, under certain deposition modes, the initial nickel films at room temperature have a saturation magnetization by an order of magnitude lower than that of nickel, and after thermal annealing at a temperature of 723 K, they exhibit magnetic anisotropy perpendicular to the surface. It is shown that the reduced value of the saturation magnetization is associated with a significant (3%) tensile deformation of the crystal lattice of nickel. It is found that the perpendicular magnetic anisotropy in the annealed films is due to the presence of tensile macro-stresses because of the differences in the thermal expansion coefficients of the film and the substrate

Formation of Pores in Thin Germanium Films under Implantation by Ge⁺ Ions

© 2020, Pleiades Publishing, Ltd. Abstract: Results are presented of a study of the morphology of germanium films nanostructured by ion implantation. Film samples were grown by magnetron sputtering in an ultrahigh-vacuum installation and then irradiated with 40 keV Ge+ ions at fluences in the range of (1.8–8) × 1016 ions/cm2. Scanning electron microscopy demonstrated that vacancy complexes with diameters of ~50–150 nm are gradually formed in the bulk of implanted germanium with increasing implantation fluence. After a certain implantation fluence is reached, the complexes emerge on the surface, thereby forming a developed surface profile of the irradiated films