DEPHASING IN PRESENCE OF A MAGNETIC FIELD

2007 ◽  
Vol 06 (03n04) ◽  
pp. 261-264 ◽  
Author(s):  
A. V. GERMANENKO ◽  
V. A. LARIONOVA ◽  
I. V. GORNYI ◽  
G. M. MINKOV
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Relaxation Rate ◽  
Negative Magnetoresistance ◽  
Phase Relaxation ◽  
Quasi Momentum ◽  
Fitting Procedure ◽  
Electron Interference ◽  
Momentum Relaxation ◽  
The Magnetic Field

Effect of the magnetic field on the rate of phase breaking is studied. It is shown that the magnetic field resulting in the decrease of phase relaxation rate [Formula: see text] makes the negative magnetoresistance due to suppression of the electron interference to be smoother in shape and lower in magnitude than that found with constant [Formula: see text]-value. Nevertheless our analysis shows that experimental magnetoconductance curves can be well fitted by the Hikami–Larkin–Nagaoka expression.1 The fitting procedure gives the value of τ/τϕ, where τ is the quasi-momentum relaxation time, which is close to the value of τ/τϕ(B = 0) with an accuracy of 25% or better when the temperature varies within the range from 0.4 to 10 K. The value of the prefactor α found from this procedure lies within the interval 0.9–1.2.

Negative magnetoresistance of polymer nanocomposites on the basis of PP + Fe3O4 and PVDF + Fe3O4 in the magnetic field

2018 ◽  
Vol 537 (1) ◽  
pp. 191-197 ◽  
Author(s):  
M. A. Ramazanov ◽  
A. M. Maharramov ◽  
Luca Di Palma ◽  
H. A. Shirinova ◽  
F. V. Hajiyeva ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Polymer Nanocomposites ◽  
Negative Magnetoresistance ◽  
The Magnetic Field

emperature Dependence of the Magnetoresistance Effect in Metals

2012 ◽  
Vol 67 (8-9) ◽  
pp. 498-508
Author(s):  
Stanisław Olszewski
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Metal Temperature ◽  
Time Increase ◽  
Electric Conduction ◽  
Magnetoresistance Effect ◽  
Metal Sample ◽  
The Magnetic Field

The paper examines a well-known experimental property of increase of the magnetoresistance effect in a metal observed with a decrease of the metal temperature. This property is explained by the fact that magnetoresistance is a quantity proportional to the relaxation time of the electric conduction of the metal sample which is a parameter observed in the absence of the magnetic field. Since the electric conduction, as well as the corresponding relaxation time, increase with the lowering of temperature, they provide us necessarily with an increase of magnetoresistance. The phenomenon is investigated quantitatively in this paper for numerous metal cases taken as examples.

MAGNETORESISTANCE IN COPPER

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4434-4441
Author(s):  
SHIGEJI FUJITA ◽  
NEBI DEMEZ ◽  
JEONG-HYUK KIM ◽  
H. C. HO
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Kinetic Theory ◽  
Anisotropic Magnetoresistance ◽  
Magnetic Field Direction ◽  
Conduction Electrons ◽  
Fcc Lattice ◽  
A Charge ◽  
The Magnetic Field ◽  
Cyclotron Mass

The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e2ncτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, nc the density of the conduction electrons, and τ the relaxation time. The density nc depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

Multiple-relaxation-time lattice Boltzmann study of the magnetic field effects on natural convection of non-Newtonian fluids

2017 ◽  
Vol 28 (11) ◽  
pp. 1750138 ◽  
Author(s):  
Xuguang Yang ◽  
Lei Wang
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Power Law ◽  
Lattice Boltzmann ◽  
Hartmann Number ◽  
Magnetic Field Effects ◽  
Multiple Relaxation Time ◽  
Number Formula ◽  
Power Law Index ◽  
The Magnetic Field

In this paper, the magnetic field effects on natural convection of power-law non-Newtonian fluids in rectangular enclosures are numerically studied by the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM). To maintain the locality of the LBM, a local computing scheme for shear rate is used. Thus, all simulations can be easily performed on the Graphics Processing Unit (GPU) using NVIDIA’s CUDA, and high computational efficiency can be achieved. The numerical simulations presented here span a wide range of thermal Rayleigh number ([Formula: see text]), Hartmann number ([Formula: see text]), power-law index ([Formula: see text]) and aspect ratio ([Formula: see text]) to identify the different flow patterns and temperature distributions. The results show that the heat transfer rate is increased with the increase of thermal Rayleigh number, while it is decreased with the increase of Hartmann number, and the average Nusselt number is found to decrease with an increase in the power-law index. Moreover, the effects of aspect ratio have also investigated in detail.

Bewegungen der CH3-Gruppen in Methyl-Naphthalin-Kristallen

1972 ◽  
Vol 27 (1) ◽  
pp. 42-50 ◽  
Author(s):  
J. U. Von Schütz ◽  
H. C. Wolf
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Activation Energies ◽  
Rotational Barrier ◽  
Proton Relaxation ◽  
Methyl Groups ◽  
Hindered Rotation ◽  
Proton Relaxation Time ◽  
Methyl Naphthalene ◽  
The Magnetic Field

Abstract The longitudinal proton relaxation time T1 in methyl naphthalene crystals, differing in the arrangement and number of the substituted CH3 groups, was measured as a function of the temperature above 77 °K and the magnetic field between 0.9 and 20 kOe. The results can be described by hindered rotation of the methyl groups with the jumping times and activation energies strongly dependent on the group arrangement. In the β-position the rotational barrier of 0.8 kcal/mol is predominantly determined by the infermolecular interaction, whereas in the case of the a-position and for adjacent CH3’s the hindering potential of 2.4 kcal/mol arises largely from the intramolecular term.

scholarly journals Quantitative Analysis of the Specific Absorption Rate Dependence on the Magnetic Field Strength in ZnxFe3−xO4 Nanoparticles

2020 ◽  
Vol 21 (20) ◽  
pp. 7775
Author(s):  
Mohamed Alae Ait Kerroum ◽  
Cristian Iacovita ◽  
Walid Baaziz ◽  
Dris Ihiawakrim ◽  
Guillaume Rogez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Large Diameter ◽  
Precipitation Method ◽  
Magnetization Relaxation ◽  
Specific Absorption ◽  
The Magnetic Field ◽  
Néel Relaxation

Superparamagnetic ZnxFe3−xO4 magnetic nanoparticles (0 ≤ x < 0.5) with spherical shapes of 16 nm average diameter and different zinc doping level have been successfully synthesized by co-precipitation method. The homogeneous zinc substitution of iron cations into the magnetite crystalline structure has led to an increase in the saturation magnetization of nanoparticles up to 120 Am2/kg for x ~ 0.3. The specific absorption rate (SAR) values increased considerably when x is varied between 0 and 0.3 and then decreased for x ~ 0.5. The SAR values are reduced upon the immobilization of the nanoparticles in a solid matrix being significantly increased by a pre-alignment step in a uniform static magnetic field before immobilization. The SAR values displayed a quadratic dependence on the alternating magnetic field amplitude (H) up to 35 kA/m. Above this value, a clear saturation effect of SAR was observed that was successfully described qualitatively and quantitatively by considering the non-linear field’s effects and the magnetic field dependence of both Brown and Neel relaxation times. The Neel relaxation time depends more steeply on H as compared with the Brown relaxation time, and the magnetization relaxation might be dominated by the Neel mechanism, even for nanoparticles with large diameter.

Cyclotron resonance in copper by a calorimetric method

1967 ◽  
Vol 296 (1447) ◽  
pp. 476-497 ◽  
Keyword(s):  
Magnetic Field ◽  
Cyclotron Resonance ◽  
Skin Depth ◽  
Negative Magnetoresistance ◽  
Calorimetric Method ◽  
Substitution Method ◽  
Resonant Orbits ◽  
Retardation Effects ◽  
The Magnetic Field

Azbel’-Kaner cyclotron resonance in copper at 136 Gc/s has been observed by a calorimetric method. Masses are presented with the magnetic field lying in a (112) plane and tipping effects investigated with the magnetic field along a <111> direction. Beyond a certain tip angle, the absorption exhibits a pronounced ‘negative magnetoresistance’ due to the removal of non­-stationary resonant orbits by tipping from the skin depth, and at smaller tip angles the resonant minima shift to lower fields as expected. The spectrometer was calibrated by a substitution method and the amplitude of the oscillations compared with theoretical estimates. Finally, a pronounced rise in absorption at low fields was observed, and arguments are presented that this is due to retardation effects.

scholarly journals Incoherent hydrodynamics of density waves in magnetic fields

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Aristomenis Donos ◽  
Christiana Pantelidou ◽  
Vaios Ziogas
Keyword(s):  
Magnetic Field ◽  
Optical Properties ◽  
Finite Temperature ◽  
Chemical Potential ◽  
Density Wave ◽  
Density Waves ◽  
Hydrodynamic Modes ◽  
Momentum Relaxation ◽  
Effective Theories ◽  
The Magnetic Field

Abstract We use holography to derive effective theories of fluctuations in spontaneously broken phases of systems with finite temperature, chemical potential, magnetic field and momentum relaxation in which the order parameters break translations. We analytically construct the hydrodynamic modes corresponding to the coupled thermoelectric and density wave fluctuations and all of them turn out to be purely diffusive for our system. Upon introducing pinning for the density waves, some of these modes acquire not only a gap, but also a finite resonance due to the magnetic field. Finally, we study the optical properties and perform numerical checks of our analytical results. A crucial byproduct of our analysis is the identification of the correct current which describes the transport of heat in our system.

Sign in / Sign up

Export Citation Format

Share Document