72 research outputs found
Electrical and galvanomagnetic properties of AuAl2+6%Cu intermetallic compounds at low temperatures
The AuAl2 intermetallic compounds are of substantial interest in view of their application potential. The investigated intermetallics AuAl 2+6%Cu were prepared from fine powders of AuAl2 and Cu by vacuum sputtering on a glass substrate and consisted of films with a thickness of about one micrometer. The films were annealed. The temperature and field dependence of the electroresistivity, the magnetoresistivity and the Hall effect of AuAl2+6%Cu films were measured in the temperature interval from 4.2 to 100 K and at magnetic fields of up to 15 T. We demonstrate that the temperature dependence of the electroresistivity has a minimum at T = 20 K and a metallic behavior above this temperature. The magnetoresistivity is very small (less then 1%), positive at low temperatures and negative above 12 K. The Hall coefficient is positive, which corresponds to the holes in a one zone model with a charge carrier concentration of about 1.6 1020 cm-3. © Published under licence by IOP Publishing Ltd
Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys
Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler
alloys of CoYZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn,
Sb) were studied in the temperature range 4.2--900 K and in magnetic fields of
up to 100 kOe. It was found that varying Y in affects strongly the electric
resistivity and its temperature dependence , while this effect is not
observed upon changing Z. When Y is varied, extrema (maximum or minimum) are
observed in near the Curie temperature . At , the
behavior can be ascribed to a change in electronic energy spectrum
near the Fermi level. The coefficients of the normal and anomalous Hall effect
were determined. It was shown that the latter coefficient, , is related to
the residual resistivity by a power law with
the spontaneous magnetization. The exponent was found to be 1.8 for
CoFeZ alloys, which is typical for asymmetric scattering mechanisms, and
2.9 for CoYAl alloys, which indicates an additional contribution to the
anomalous Hall effect. The temperature dependence of resistivity at low
temperatures is analyzed and discussed in the framework of the two-magnon
scattering theory.Comment: Invited Report on the Moscow International Symposium on Magnetism
MISM-2017, pdf only, 6 pages, J. Magn. Magn. Mater., in pres
Peculiarities of the electronic and magnetic characteristics in Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) Heusler alloys close to the half-metallic ferromagnets and spin gapless semiconductors
The Hall Effect and magnetization of Heusler alloys Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) were measured at T = 4.2 K and 300 K in magnetic fields of up to 100 kOe as well as the temperature dependence of the electroresistivity from 4.2 to 300 K. The normal and anomalous Hall coefficients, saturation magnetization, residual resistivity, type and concentration of current carriers and their mobility were obtained. It was demonstrated that there is a clear correlation between the electronic and magnetic parameters obtained, depending on the number of valence electrons z, at the transition from Co2TiSi (z=26) to Co2NiSi (z=32). The observed peculiarities of electronic and magnetic parameters may be due to the appearance of the states of the half-metallic ferromagnet and/or spin gapless semiconductor. © Published under licence by IOP Publishing Ltd.This work was carried out as part of the state task of the Russian Ministry of Education and Science (themes “Spin”,No. AAAA-A18-118020290104-2) with partial support from the Russian Foundation for Basic Research (projects Nos. 18-32-00686 and 18-02-00739) and the Government of the Russian Federation (Act No. 211, contract No. 02.A03.21.0006)
Effect of Various Infusion Solutions on Microrheology
Objective: to evaluate the in vitro and in vivo effects of various infusion solutions on red blood cell rheology in the early posttraumatic period. Material and methods. The in vitro study assessed crystalloids, albumin, dextrans, modified gelatin, and different generations of hydroxyethyl starches (HES). The preparations were added to blood in a 1:10 dilution; before and after their addition, the values of erythrocyte aggregation and erythrocyte deformability were estimated. The in vivo study covered 59 patients with severe concomitant injury, who were divided into 3 groups: 1) those who received crystalloids only; 2) those who had crystalloids + 6% HES 130/0.42; 3) those who had crystalloids + gelofusine. The same parameters of red blood cell rheology were estimated as in the in vitro study. Results. Albumin, repolyglycan, and HES 130/0.42 were found to have the most pronounced disaggregatory effect in vitro. At the same time, polyglycan, gelofusine, and HES 450/0.7 in particular, enhanced erythrocyte aggregation. In vitro, albumin, HES 130/0.42, and HES 200/0.5 exerted the most beneficial effect on erythrocyte deformability whereas dextrans made the latter worse and HES 450/0.7 and gelofusine failed to have a considerable effect on it. The early posttraumatic period was marked by progressive erythrocyte hyperaggregation and phasic deformability changes. Significant microrheological disorders persisted in the patients on infusion therapy with crystalloid solutions only. Addition of HES 130/0.42 to infusion therapy improved the deformability of erythrocytes and lowered their aggregation. The use of gelofusine as a component of infusion therapy caused a moderate increase in erythrocyte aggregation. Key words: infusion therapy, erythrocyte deformability, erythrocyte aggregation
Electrical and optical properties of a PtSn 4 single crystal
A topological semimetal PtSn4 single crystal was grown by method of crystallization from a solution in a melt. Then the electrical resistivity and galvanomagnetic properties (magnetoresistivity and the Hall effect) were studied in the temperature range from 4.2 to 80 K and in magnetic fields up to 100 kOe. The optical measurements were carried out at room temperature. The residual resistivity is shown to be low enough and amount to ∼ 0.5 μOhm•cm. The temperature dependence of the electrical resistivity has a metallic type, increasing monotonically with temperature. A sufficiently large magnetoresistance of 750% is observed. The majority carriers are supposed to be holes with a concentration of ∼ 6.8•10 21 cm -3 and mobility of ∼ 1950 cm 2 /Vs at T = 4.2 K as a result of the Hall effect studies. The optical properties of PtSn 4 have features characteristic of "bad" metals. © 2019 Published under licence by IOP Publishing Ltd.This work was partly supported by the state assignment of Russia (theme “Spin” No. АААА-А18-18020290104-2 and theme “Electron” No. АААА-А18-118020190098-5), by the RFBR (project No.17-52-52008) and by the Government of the Russian Federation (state contract No. 02.A03.21.0006)
Impact of liquid metal surface on plasma-surface interaction in experiments with lithium and tin capillary porous systems
The lithium and tin capillary-porous systems (CPSs) were tested with steady-state plasma in the PLM plasma device which is the divertor simulator with plasma parameters relevant to divertor and SOL plasma of tokamaks. The CPS consists of tin/lithium tile fixed between two molybdenum meshs constructed in the module faced to plasma. Steady-state plasma load of 0.1 - 1 MW/m(2) on the CPS during more than 200 min was achieved in experiments on PLM which is a modeling far scrapeoff- layer and far zone of divertor plasma of a large tokamak. The heating of the CPS was controlled remotely including biasing technique which allows to regulate evaporated metal influx to plasma. After exposure, the materials of the tin and lithium CPSs were inspected and analyzed with optic and scanning electron micriscopy. Experiments have demonstrated sustainability of the tin and lithium CPSs to the high heat steady state plasma load expected in a large scale tokamak. The effect of evaporated lithium and tin on the plasma transport/radiation was studied with spectroscopy to evaluate changes of plasma properties and plasma-surface interaction
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