A Quantum Percolation Model for Magnetoconductance of Granular Metal Films

1990 ◽  
Vol 195 ◽  
Author(s):  
Zhao-Qing Zhang ◽  
Ping Sheng
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Metal Films ◽  
Percolation Model ◽  
Recent Experimental Data ◽  
Quantum Percolation ◽  
Sign Change ◽  
Strong Scattering ◽  
The Magnetic Field

ABSTRACTA quantum percolation model is introduced to study the magnetoconductance of granular metal films. This model incorporates the granular property of the films and enables us to study the magnetoconductance in the strong scattering regime. Our calculations show a sign change in magnetoconductance as the temperature varies. There also exist oscillations in the magnetoconductance as the magnetic field is increased. Both observations are consistent with some recent experimental data.

Doppler-Shifted Cyclotron Resonance in Thin Metal Films

1972 ◽  
Vol 50 (18) ◽  
pp. 2122-2137
Author(s):  
R. Turner ◽  
J. F. Cochran
Keyword(s):  
Magnetic Field ◽  
Metal Films ◽  
Thin Metal Film ◽  
Thin Metal ◽  
Free Electrons ◽  
Fermi Surfaces ◽  
First Order ◽  
Simple Quantum ◽  
The Magnetic Field ◽  
Good Agreement

According to Van Gelder the microwave absorption by a thin metal film in the presence of a static magnetic field normal to the film contains a series of peaks as the magnetic field is varied. In the present paper it is argued that these peaks correspond to Doppler-shifted cyclotron resonances of the carriers in the metal due to the quantization of electron momenta normal to the plane of the film. A simple quantum calculation is presented for the case of free electrons where the film is thin enough that to first order the microwave fields within are determined only by the boundary conditions and Maxwell's equations. The quantum expression is in good agreement with the absorption calculated using semiclassical arguments which can be readily extended to more complicated Fermi surfaces.

ELECTROMAGNETIC FIELDS IN AN N‐LAYER ANISOTROPIC HALF‐SPACE

Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 668-677 ◽  
Author(s):  
Douglas P. O’Brien ◽  
H. F. Morrison
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Plane Wave ◽  
Half Space ◽  
Electric Fields ◽  
Field Measurements ◽  
Large Scatter ◽  
Tensor Impedance ◽  
The Magnetic Field ◽  
Made In

From Maxwell’s equations and Ohm’s law for a horizontally anisotropic medium, it may be shown that two independent plane wave modes propagate perpendicular to the plane of the anisotropy. Boundary conditions at the interfaces in an n‐layered model permit the calculation, through successive matrix multiplications, of the fields at the surface in terms of the fields propagated into the basal infinite half space. Specifying the magnetic field at the surface allows the calculation of the resultant electric fields, and the calculation of the entries of a tensor impedance relationship. These calculations have been programmed for the digital computer and an interpretation of impedances obtained from field measurements may thus be made in terms of the anisotropic layering. In addition, apparent resistivities in orthogonal directions have been calculated for specific models and compared to experimental data. It is apparent that the large scatter of observed resistivities can be caused by small changes in the polarization of the magnetic field.

Formation and dynamics of easy orientation axis in magnetic field on PVCN-F surface

2006 ◽  
Vol 14 (4) ◽  
Author(s):  
O. Buluy ◽  
Y. Reznikov ◽  
K. Slyusarenko ◽  
M. Nobili ◽  
V. Reshetnyak
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Easy Axis ◽  
Partial Relaxation ◽  
Soft Surface ◽  
Orientation Axis ◽  
The Magnetic Field ◽  
Additional Assumptions

AbstractWe describe the experiments on a magnetically-induced drift of the easy axis on a soft surface of photoaligning material fluoro-polyvinyl-cinnamate. We found unexpected partial relaxation of the drift of the easy axis after switching the magnetic field off. This relaxation cannot be explained in a framework of the existing models and requires additional assumptions about the drift process. We propose a model that explains the experimental data suggesting elastic-like behaviour of the polymer fragments during the drift of the easy axis.

scholarly journals Effect of a stochastic electric field on plasma confinement in FTU

2016 ◽  
Vol 31 (02) ◽  
pp. 1650005 ◽  
Author(s):  
Roberto Martorelli ◽  
Giovanni Montani ◽  
Nakia Carlevaro
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Electric Field ◽  
Uniform Magnetic Field ◽  
Planck Equation ◽  
Plasma Confinement ◽  
Stochastic Field ◽  
Magnetically Confined ◽  
The Magnetic Field ◽  
Plasma Profile

We discuss a stochastic model for the behavior of electrons in a magnetically confined plasma having axial symmetry. The aim of the work is to provide an explanation for the density limit observed in the Frascati Tokamak Upgrade (FTU) machine. The dynamical framework deals with an electron embedded in a stationary and uniform magnetic field and affected by an orthogonal random electric field. The behavior of the average plasma profile is determined by the appropriate Fokker–Planck equation associated to the considered model and the disruptive effects of the stochastic electric field are shown. The comparison between the addressed model and the experimental data allows to fix the relevant spatial scale of such a stochastic field. It is found to be of the order of the Tokamak micro-physics scale, i.e. few millimeters. Moreover, it is clarified how the diffusion process outlines a dependence on the magnetic field as [Formula: see text].

Oscillatory Angular Dependence of Exchange Bias for Epitaxial NiO-Co (001) Bilayers

2001 ◽  
Vol 674 ◽  
Author(s):  
S. Dubourg ◽  
J.F. Bobo ◽  
B. Warot ◽  
E. Snoeck ◽  
J.C. Ousset
Keyword(s):  
Magnetic Field ◽  
Exchange Bias ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Field Application ◽  
Zero Field ◽  
Sign Change ◽  
Realistic Description ◽  
Sputter Deposited ◽  
The Magnetic Field

ABSTRACTWe have sputter-deposited NiO-Co bilayers on MgO (001) substrates. NiO grows epitaxially on MgO at 900°C and subsequently the room deposited 80 Åthick Co films have a fcc crystal structure in epitaxy with the oxide underlayer. These samples were warmed up to 300° C and then zero-field or field cooled through the NiO Néel temperature (a 300 Oe magnetic field was applied along the [100] or the [110] MgO axis). Magnetic hysteresis loops were obtained by magneto-optical Kerr effect, the magnetic field being oriented in the plane of the substrate for various angles α with respect to the [100] direction. The usually expected behavior for such experiments is a smooth angular α dependence of the exchange bias HE close to a cosine with only one sign change over 180°. The high crystallographic coherence of our NiO/Co bilayers induces a very unusual oscillatory HE (α) dependence with several sign changes according to the NiO axis field application. Despite of the Co magnetization switching mechanism which is not a pure coherent rotation, we propose a Stoner-Wohlfhart model including four fold anisotropy and unidirectional exchange anisotropy giving a realistic description of these typical magnetic properties.

Phonon properties of delafossite multiferroic compound CuFeO2. Comparison with CuCrO2

2019 ◽  
Vol 33 (12) ◽  
pp. 1950141
Author(s):  
A. T. Apostolov ◽  
I. N. Apostolova ◽  
J. M. Wesselinowa
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Phase Transition ◽  
Dopant Concentration ◽  
Phonon Energy ◽  
Function Technique ◽  
Ion Doping ◽  
Increasing Temperature ◽  
The Magnetic Field ◽  
Phonon Properties

The temperature, magnetic field and ion doping dependence of the phonon properties of CuFeO2 are studied on the basis of a microscopic model and using Green’s function technique. The phonon energy decreases with increasing temperature, whereas the phonon damping increases. There is a kink at the phase transition temperature [Formula: see text] which shows the influence of the magnetic field on the phonon properties. The kinks vanish by applying an external magnetic field. By doping of ions with different radius compared to the Fe ion, the phonon energy in CuFeO2 can increase (Ga) or decrease (Sc) with increasing dopant concentration, whereas the damping is always enhanced. The results are compared with those of CuCrO2. Some discrepancies in the literature are discussed. The observed results are in qualitative agreement with the experimental data.

Upper Critical Field and Irreversibility Line in Bi2Sr2CuO6+δ/CaCuO2 Superconducting Superlattices Obtained by MBE

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2767-2772
Author(s):  
Matteo Salvato ◽  
Carmine Attanasio ◽  
Gerardina Carbone ◽  
Rosalba Fittipaldi ◽  
Tiziana Di Luccio ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Thin Films ◽  
Phase Diagrams ◽  
Applied Magnetic Field ◽  
Three Dimensional ◽  
Upper Critical Field ◽  
Resistivity Measurements ◽  
T Phase ◽  
The Magnetic Field

Resistivity measurements in external applied magnetic field up to 8.5T have been performed on Bi2Sr2CuO6+δ/CaCuO2 superconducting superlattices obtained by MBE. The magnetic field (H) vs. temperature (T) phase diagrams have been determined and the experimental data have been compared with that obtained in the case of Bi2Sr2CuO6+δ thin films deposited with the same technique. A reduction of the anisotropy has been obtained in the case of the superlattices with respect to the case of Bi2Sr2CuO6+δ thin films and a three dimensional behavior has been observed by paraconductivity measurements.

INVESTIGATING THE TIME DEPENDENCE OF THE MR EFFECT

2007 ◽  
Vol 21 (28n29) ◽  
pp. 4832-4840 ◽  
Author(s):  
FERNANDO D. GONCALVES ◽  
J. DAVID CARLSON
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Response Time ◽  
Time Dependence ◽  
Dwell Time ◽  
High Shear ◽  
Proposed Model ◽  
Mr Effect ◽  
The Magnetic Field ◽  
Field Strengths

Magnetorheological fluids are known to respond in a matter of milliseconds to the application of a magnetic field. To date, however, very little work has been done to study the time dependence of the MR response. The purpose of this study is to investigate the response time of the fluid. Experiments were conducted on a high shear rate rheometer capable of fluid speeds in excess of 35 m/s. With an MR valve length of 6.35 mm, the resulting dwell times were as low as 0.18 ms. For each of three magnetic field strengths, a reduction in yield stress is observed as dwell time decreases. A model is proposed to represent the time response of the fluid to the application of the magnetic field. The experimental data and the proposed model are used to identify the response time of the fluid for each field strength. Results indicate that as the magnetic field increases, the response time of the MR fluid decreases. For the range of magnetic field strengths considered in this study the response time of the fluid ranged from 0.24 ms to 0.19 ms.

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