84 research outputs found
Magnetic States and Electronic Properties of Manganese-Based Intermetallic Compounds MnYAl and MnZ (Y = V, Cr, Fe, Co, Ni; Z = Al, Ge, Sn, Si, Pt)
We present a brief review of experimental and theoretical papers on studies
of electron transport and magnetic properties in manganese-based compounds
MnYZ and MnZ (Y = V, Cr, Fe, Co, Ni, etc.; Z = Al, Ge, Sn, Si, Pt,
etc.). It has been shown that in the electronic subsystem of MnYZ
compounds, the states of a half-metallic ferromagnet and a spin gapless
semiconductor can arise with the realization of various magnetic states, such
as a ferromagnet, a compensated ferrimagnet, and a frustrated antiferromagnet.
Binary compounds MnZ have the properties of a half-metallic ferromagnet and
a topological semimetal with a large anomalous Hall effect, spin Hall effect,
spin Nernst effect, and thermal Hall effect. Their magnetic states are also
very diverse: from a ferrimagnet and an antiferromagnet to a compensated
ferrimagnet and a frustrated antiferromagnet, as well as an antiferromagnet
with a kagome-type lattice. It has been demonstrated that the electronic and
magnetic properties of such materials are very sensitive to external influences
(temperature, magnetic field, external pressure), as well as the processing
method (cast, rapidly quenched, nanostructured, etc.). Knowledge of the
regularities in the behavior of the electronic and magnetic characteristics of
MnYAl and MnZ compounds can be used for applications in micro- and
nanoelectronics and spintronics.Comment: Review paper, 27 page
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
НЕИНВАЗИВНАЯ ВЕНТИЛЯЦИЯ ЛЕГКИХ У БОЛЬНЫХ С ТЯЖЕЛОЙ ОСЛОЖНЕННОЙ ТОРАКАЛЬНОЙ ТРАВМОЙ
Summary. The objective of this prospective study was to investigate the efficiency of noninvasive ventilation in patients with severe blunt thoracic trauma, muliple rib fractures and acute hypoxemic respiratory failure. 73 patients were randomized into 2 groups (36 patients in the study group and 37 patientsn the control group). All of them needed in mechanical ventilation. The main group patients were ventilated via face or nasal mask. The control group patients were ventilated via endotracheal tube. We found that noninvasive ventilation improved lung functions and reduced respiratory failuren 61.1 % of the patients without tracheal intubation. Noninvasive ventilation was reliably associated with reduction in lung complication rate, duraion of treatment and mortality. Unsuccessful attempts of noninvasive ventilation were not associated with worse outcomes (frequency of pulmonary complications, duration of treatment, mortality). Based on analysis of these parameters and periods of unsuccessful noninvasive ventilation we developed prognostic criteria and critical periods of unsuccessful noninvasive ventilation. Conclusion: noninvasive ventilation allowed reduction in risk of poor outcomes in particular group of patients with severe and complicated thoracic trauma
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
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)
- …