scholarly journals Туннельная проводимость и туннельное магнитосопротивление пленок Fe-SiO: корреляция магнитотранспортных и магнитных свойств

2019 ◽  
Vol 61 (7) ◽  
pp. 1262
Author(s):  
Д.А. Балаев ◽  
А.Д. Балаев
Keyword(s):  
Activation Energy ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
Magnetic Method ◽  
Tunnel Mechanism ◽  
Giant Magnetoresistive Effect ◽  
Temperature Dependences ◽  
Magnetoresistive Effect ◽  
Dielectric Region ◽  
Good Agreement

The paper presents the results of a study of the electrical properties of a system of nanogranular amorphous Fe-SiO films with a SiO concentration from 0 to 92 Vol.%. For samples with a low SiO content, metallic conductivity takes place. With an increase of the dielectric content, a concentration transition of conduction from the metallic regime to the tunnel regime at a dielectric concentration x  0.6 is observed. At the same concentration, a transition ferromagnet - superparamagnet occurs, which was previously investigated by the magnetic method. For compositions corresponding to the dielectric region, the temperature dependences of the electrical resistance (T) follow the law (T) ~ exp(2(С/kT)1/2), which is typical for the tunnel mechanism of conductivity. Estimation of the sizes of metal granules from the values of the tunneling-activation energy C showed a good agreement with the sizes obtained earlier from the analysis of magnetic properties. In the dielectric range of the compositions, a giant magnetoresistive effect was obtained, reaching 25% at low temperatures.

scholarly journals A Peierls-Nabarro Model for Kink-Pair Generation in Screw Dislocations at Low Temperatures

1998 ◽  
Vol 538 ◽  
Author(s):  
A.H.W. Ngan
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Plane Strain ◽  
Low Temperatures ◽  
Screw Dislocations ◽  
Kink Pair ◽  
Bcc Lattice ◽  
Pair Generation ◽  
Experimental Findings ◽  
Good Agreement

AbstractKink-pair generation in three-fold screw dislocations in the bcc lattice is investigated within the framework of the generalised Peierls-Nabarro model. Using a piece-wise plane strain approximation, the apparent activation energy is predicted to vary with stress in a parabolic manner which is in good agreement with experimental findings.

Viscosity of Liquid Nanocrystalline Alloys

2021 ◽  
Vol 880 ◽  
pp. 35-41
Author(s):  
V.S. Tsepelev ◽  
Yuri N. Starodubtsev ◽  
Nadezhda P. Tsepeleva
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
Viscous Flow ◽  
Critical Point ◽  
Free Volume ◽  
Electrical Resistance ◽  
Kinematic Viscosity ◽  
Chemical Compositions ◽  
Cooling Stage ◽  
Temperature Dependences

Temperature dependences of the kinematic viscosity, density, and electrical resistivity of Fe72.5Cu1Nb2Mo1.5Si14B9 and Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 multicomponent melts have been studied. We found different behavior of the temperature dependences of viscosity near the critical point Tk = 1760 K during heating, which is associated with different chemical compositions of the clusters in the melt. In the cooling stage, the activation energy of the viscous flow for these two melts is the same and equal to 43 kJ·mol-1. At a temperature of 1720 K, the relative free volume is 5.1 and 7.5 % of the total melt volume for Fe72.5Cu1Nb2Mo1.5Si14B9 and Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 respectively. In the cooling stage, the electrical resistance of melt is higher than at the heating stage.

scholarly journals Влияние углерода на электрические свойства объемных композитов на основе окиси меди

2018 ◽  
Vol 60 (4) ◽  
pp. 677
Author(s):  
Ю.Е. Калинин ◽  
М.А. Каширин ◽  
В.А. Макагонов ◽  
С.Ю. Панков ◽  
А.В. Ситников
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistance ◽  
Low Temperatures ◽  
Ceramic Technology ◽  
Localized States ◽  
Filler Concentration ◽  
Schematic Model ◽  
Carbon Filler ◽  
The Matrix ◽  
Temperature Dependences

AbstractThe effect of carbon filler on the electrical resistance and the thermopower of copper oxide-based composites produced by ceramic technology by hot pressing has been studied. It is found that the dependences of the electrical resistivity on the filler concentration are characteristic by S-like curves that are typical of percolation systems; in this case, the resistivity decreases more substantially as the carbon content increases as compared to the decrease in thermopower value, which is accompanied by the existence of the maximum of the factor of thermoelectric power near the percolation threshold. The studies of the temperature dependences of the resistivity and the thermopower at low temperatures show that, in the range 240–300 K, the predominant mechanism of the electrotransfer of all the composites under study is the hopping mechanism. At temperatures lower than 240 K, the composites with a nanocrystalline CuO matrix have a hopping conductivity with a variable hopping distance over localized states of the matrix near the Fermi level, which is related to the conductivity over intergrain CuO boundaries. A schematic model of the band structure of nanocrystalline CuO with carbon filler is proposed on the base of the analysis of the found experimental regularities of the electrotransfer.

Kinematic Viscosity and Electrical Resistivity of a Multicomponent Melt due to Liquid–Liquid Structure Transition

2021 ◽  
Vol 904 ◽  
pp. 111-116
Author(s):  
Vladimir Tsepelev ◽  
Yuri N. Starodubtsev ◽  
Viktor V. Konashkov ◽  
Yekaterina A. Kochetkova
Keyword(s):  
Activation Energy ◽  
Electrical Resistivity ◽  
Electrical Resistance ◽  
Cluster Size ◽  
Kinematic Viscosity ◽  
Arrhenius Plot ◽  
Liquid Structure ◽  
Structure Transition ◽  
Temperature Range ◽  
Temperature Dependences

We investigated the kinematic viscosity and electrical resistivity of the multicomponent Fe74Cu1Nb1.5Mo1.5B8.5Si13.5 melt during three heating–cooling cycles. The temperature dependence of kinematic viscosity and electrical resistivity have the anomalous zones in the same temperature range and they are associated with the liquid–liquid structure transition (LLST). The anomalies were explained by changes in the activation energy and the cluster size. As the cluster size decreases, the activation energy decreases, but the viscosity and electrical resistance increase. LLST begins with the cluster dissolution, and as a result, the Arrhenius plot becomes nonlinear in the transition temperature range. After three cycles of heating–cooling, the temperature dependences of the kinematic viscosity and electrical resistance did not qualitatively change, and this allows us to conclude that LLST is thermoreversible. With an increase in the number of thermal cycles, the activation energy of viscous flow decreases, as well as the onset temperature and temperature range of LLST.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

scholarly journals Experiments at very low temperatures obtained by the magnetic method I—The production of the low temperatures

1935 ◽  
Vol 149 (866) ◽  
pp. 152-176 ◽  
Keyword(s):  
Liquid Helium ◽  
Vapour Pressure ◽  
Low Temperatures ◽  
Usual Method ◽  
Magnetic Method ◽  
Isothermal Magnetization

The lowest limit of temperature obtainable by the hitherto usual method of evaporating liquid helium lies at about 0⋅7º. At this temperature the vapour pressure of helium is already so small that it does not seem possible to proceed to appreciably lower temperatures in this way. In the course of last year the first successful experiments in attaining still lower temperatures were carried out using the magnetic method proposed by Debye and Giauque. This method is based on the possibility of diminishing considerably the entropy of some paramagnetic salts by isothermal magnetization. The subsequent demagnetization, if carried out adiabatically, then results in a lowering of the temperature.

Anisotropic giant magnetoresistive effect in the sandwich based FexNi1−x (x ≈ 0.5) and Cu

2018 ◽  
Vol 91 (12) ◽  
Author(s):  
Yurii O. Shkurdoda ◽  
Leonid V. Dekhtyaruk ◽  
Andrii G. Basov ◽  
Anatoliy P. Kharchenko ◽  
Anatoliy M. Chornous ◽  
...  
Keyword(s):  
Giant Magnetoresistive Effect ◽  
Magnetoresistive Effect

Isotopic Thermal Diffusion Factors for Helium and Neon at Low Temperatures

1963 ◽  
Vol 18 (2) ◽  
pp. 242-245 ◽  
Author(s):  
W. W. Watson ◽  
A. J. Howard ◽  
N. E. Miller ◽  
R. M. Shiffrin
Keyword(s):  
Thermal Diffusion ◽  
Low Temperatures ◽  
Quantum Corrections ◽  
Intermolecular Potential ◽  
De Vries ◽  
Lower Temperature ◽  
Improved Accuracy ◽  
Good Agreement

With an all-metal “swing separator” having unique features, thermal diffusion factors αT for He3/He4 and Ne20Ne22 have been measured with improved accuracy down to average gas temperatures T̅=136°K. For helium αT is 0.0696 ± 0.0010 at 136°K, dropping gradually to 0.0651 ±0.0010 at 313°K. These data, plus measurements by Van der Valk and de Vries at somewhat higher temperatures, agree best with values predicted by an exp-six intermolecular potential with ε/k=9.16 and α=12.7. We are extending these helium measurements down to T=4°K for the lower temperature, to detect if possible quantum corrections to the intermolecular potential. For neon αT increases from 0.0166 ± 0.0010 at 136°K to 0.0233 ± 0.0020 at 310°K, considerably higher than our previously reported values. These T. D. factors for neon are in good agreement with values calculated from an exp-six potential with ε/k = 46.0 ± 0.6 and α=13.

Temperaturabhängigkeit der statischen Dielektrizitätskonstante und des optischen Brechungsindexes von Flüssigkeiten

1975 ◽  
Vol 30 (3) ◽  
pp. 287-291 ◽  
Author(s):  
I. Gryczyński ◽  
A. Kawski
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Dipole Moment ◽  
Dipole Moments ◽  
Mixed Solvents ◽  
Temperature Changes ◽  
Temperature Dependences ◽  
Solvent Shifts ◽  
Pure And Mixed Solvents ◽  
Good Agreement

A variation of the temperature changes the static dielectric constant (ε) and the refractive index (n) of solvents and, in conjunction with the measurement of solvent shifts of absorption and fluorescence maxima, allows the investigation of dipole moment changes of solutes in the excited state. For this purpose, investigations of the temperature dependences of ε and n of some pure and mixed solvents of different polarities have been made. It is found that the excited dipole moments of indole, 1,2-dimethylindole, 2,3-dimethylindole and tryptophan obtained from the shifts of the fluorescence maxima in mixed solvents at high temperatures are in good agreement with those obtained in other ways.

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