Searcharxiv⌕ Search

arXiv subjects

C. Tannous

Publications and source records attributed to C. Tannous.

At least 37 records · Page 2Linked to original sources
arXiv2008

The Stoner-Wohlfarth model of Ferromagnetism: Dynamic and Statistical properties

The physics of magnetic state change or reversal in single domain magnetic grains (called Stoner particles) is interesting from the fundamental as well as the applied points of view. A change in magnetization can be finely tuned with a specific time variation o f an externally applied magnetic field. It may also occur naturally (without application of a field) at very low tempe rature with quantum tunneling and at higher temperature with thermal excitation. The optimal (usually shortest) time altering the magn etisation along with the smallest applied magnetic field are sought in technological applications s uch as high-density reading or writing of information, spintronics, quantum inform ation and quantum communication systems. This work reviews the magnetization change with a time dependent field and tem perature and discusses the time it takes to alter the magnetization as a function of the control parameter chosen, temperature and material parameters.

physics.class-ph↗
arXiv2007

Effect of the metal-to-wire ratio on the high-frequency magnetoimpedance of glass-coated CoFeBSi amorphous microwires

High frequency [1-500 MHz] measurements of the magnetoimpedance (MI) of glass-coated Co$_{69.4}$Fe$_{3.7}$B$_{15.9}$Si$_{11}$ microwires are carried out with various metal-to-wire diameter ratios. A twin-peak, anhysteretic behaviour is observed as a function of magnetic field. A maximum in the normalized impedance, $ΔZ$/$Z$, appears at different values of the frequency $f$, 125, 140 and 85 MHz with the corresponding diameter ratio $p$ = 0.80, 0.55 and 0.32. We describe the measurement technique and interpret our results with a thermodynamic model that leads to a clearer view of the effects of $p$ on the maximum value of MI and the anisotropy field. The behavior of the real and imaginary components of impedance is also investigated; they display a resonance that becomes a function of the DC field $H_{DC}$ for values larger or equal to $H_{K}$ the circumferential anisotropy field for each $p $ value. These results are interpreted in terms of a rotation model of the outer shell magnetization.

cond-mat.mtrl-sci↗
arXiv2007

The Canonical Function Method and its applications in Quantum Physics

The Canonical Function Method (CFM) is a powerful method that solves the radial Schrödinger equation for the eigenvalues directly without having to evaluate the eigenfunctions. It is applied to various quantum mechanical problems in Atomic and Molecular physics with presence of regular or singular potentials. It has also been developed to handle single and multiple channel scattering problems where the phaseshift is required for the evaluation of the scattering cross-section. Its controllable accuracy makes it a valuable tool for the evaluation of vibrational levels of cold molecules, a sensitive test of Bohr correspondance principle and a powerful method to tackle local and non-local spin dependent problems.

quant-ph↗
arXiv2006

Magnetic domain-walls and the relaxation method

The relaxation method used to solve boundary value problems is applied to study the variation of the magnetization orientation in several types of domain walls that occur in ferromagnetic materials. The algorithm is explained and applied to several cases: the Bloch wall in bulk magnetic systems, the radial wall in cylindrical wires and the Néel wall in thin films

physics.class-ph↗
arXiv2005

Helical anisotropy and magnetoimpedance of CoFeSiB wires under torsional stress

Recent measurements of the magnetoimpedance (at a fixed frequency of 1 MHz) of cobalt-rich wires subjected to torsion stress show an asymmetry as a function of torsion angle stemming from residual anisotropies induced during wire fabrication. We interpret these measurements with a simple model based on the competition between a circumferential magnetic anisotropy and another one induced by torsional and residual stress. This allows extraction of the physical parameters of the wire and explains the positive and negative torsion cases. The agreement between theoretical and experimental results provides a firm support for the model describing the behaviour of the anisotropy field versus static magnetic field for all torsion angles.

cond-mat.mtrl-sci↗
arXiv2004

Metal-to-glass ratio and the Magneto-Impedance of glass-covered CoFeBSi microwires at high frequencies

High frequency [1-500 MHz] measurements of the Magneto-Impedance (MI) of glass-covered Co$_{69.4}$Fe$_{3.7}$B$_{15.9}$Si$_{11}$ microwires are carried out with various metal-to-wire diameter ratios. A twin-peak, anhysteretic behaviour is observed as a function of magnetic field. A maximum in $ΔZ/Z$ appears at different values of the frequency $f$, 125, 140 and 85 MHz with the corresponding diameter ratio $p$ = 0.80, 0.55 and 0.32. We describe the measurement technique and interpret our results with a thermodynamic model that leads to a clearer view of the effects of $p$ on the maximum value of MI and the anisotropy field.

cond-mat.mtrl-sci↗
arXiv2003

Frequency and Phase Noise in Non-Linear Microwave Oscillator Circuits

We have developed a new methodology and a time-domain software package for the estimation of the oscillation frequency and the phase noise spectrum of non-linear noisy microwave circuits based on the direct integration of the system of stochastic differential equations representing the circuit. Our theoretical evaluations can be used in order to make detailed comparisons with the experimental measurements of phase noise spectra in selected oscillating circuits.

physics.comp-ph↗
arXiv2003

The Pedagogy of the p-n Junction: Diffusion or Drift?

The majority of current textbooks on device physics at the undergraduate level derive the diode equation based on the diffusion of injected minority carriers. Generally the drift of the majority carriers, or the extent of drift, is not discussed and the importance of drift in the presence of a field in the neutral regions is almost totally ignored. The assumptions of zero field in the neutral regions and conduction by minority carrier diffusion lead to a number of pedagogical problems and paradoxes for the student. The purpose of this paper is to address the pedagogical problems and paradoxes apparent in the current treatment of conduction in the pn junction as it appears in the majority of texts.

physics.ed-ph↗
arXiv2003

Giant magnetoimpedance in Vitrovac amorphous ribbons over [0.3-400 MHz] frequency range

Giant magneto impedance (GMI) effect for as-cast Vitrovac$^{\textrm{\scriptsize\textregistered}}$ amorphous ribbons (Vacuumschmelze, Germany) in two configurations (parallel and normal to the ribbon axis) is studied over the frequency range [0.3-400 MHz] and under static magnetic fields -160 Oe $< H_{dc} < $+160 Oe. A variety of peak features and GMI ratio values, falling within a small field range, are observed and discussed.

cond-mat.mtrl-sci↗
arXiv2003

Generalised Modal Analysis with the Padé-Laplace transform

We present the G-MAPLE (Generalised Modal Analysis from the Poles of the Laplace Expansion) software that allows decomposing data depending on a single parameter (such as time series data) into a set of exponential functions having complex amplitudes and arguments. The novelty is that G-MAPLE determines the unknown number of exponentials in the data along with the corresponding complex amplitudes and arguments.

physics.data-an↗
arXiv2003

Giant Magneto-Impedance and its Applications

The status of Giant Magneto-Impedance effect is reviewed in Wires, Ribbons and Multilayered Soft Ferromagnetic Thin Films. After establishing the theoretical framework for the description of the effect, and the constraints any material should have in order to show the effect, experimental work in Wires, Ribbons and Multilayered Thin Films is described. Existing and potential applications of the effect in Electronics and Sensing are highlighted.

physics.ins-det↗
arXiv2002

Non-linear quantization for arbitrary distributions and applications to Medical Image Processing

We report the development of a scalar quantization approach that helps build tables of decision and reconstruction levels for any probability density function (pdf). Several example pdf's are used for illustration: Uniform, Gaussian, Laplace, one-sided Rayleigh, and Gamma (One sided and double-sided symmetrical). The main applications of the methodology are principally aimed at Multiresolution Image compression where generally the Stretched Exponential pdf is encountered. Specialising to this important case, we perform quantization and information entropy calculations from selected medical MRI (Magnetic Resonance Imaging) pictures of the human brain. The image histograms are fitted to a Stretched exponential model and the corresponding entropies are compared.

physics.med-ph↗
arXiv2002

Low energy (e,2e) ionization of Argon in the equal energy sharing geometry

Quantum Defect theory is a well established theoretical concept in modern spectroscopy. We show that this approach is useful in electron impact ionization problems where state of the art theoretical methods are presently restricted mostly to simple atomic targets. For the well documented Argon ionization case in equal energy sharing geometry the approach suggested leads to significant improvements compared to previous calculations.

quant-ph↗
arXiv2002

Distorted Waves with Exact Non-Local Exchange: a Canonical Function Approach

It is shown how the Canonical Function approach can be used to obtain accurate solutions for the distorted wave problem taking account of direct static and polarisation potentials and exact non-local exchange. Calculations are made for electrons in the field of atomic hydrogen and the phaseshifts are compared with those obtained using a modified form of the DWPO code of McDowell and collaborators: for small wavenumbers our approach avoids numerical instabilities otherwise present. Comparison is also made with phaseshifts calculated using local equivalent-exchange potentials and it is found that these are inaccurate at small wavenumbers. Extension of our method to the case of atoms having other than s-type outer shells is dicussed.

quant-ph↗
arXiv2002

Magnetic and Transport Properties of NiFe/SiO_{2}/NiFe Trilayers

Magnetic coupling between Ni_{81}Fe_{19} double thin films separated by an insulating SiO_{2} spacer layer is investigated with structural measurements, cross sectional imaging, magnetization measurements (BH loop) and transport under the conditions of variable spacer thickness ranging from 0 to 5000 Angstroms. We investigate several models to explain the coercivity variation with spacer thickness as well as the transport measurements.

cond-mat.mtrl-sci↗
arXiv2001

Direct Determination of Harmonic and Inter-modulation distortions with an application to Single Mode Laser Diodes

Harmonic and Intermodulation distortions occur when a physical system is excited with a single or several frequencies and when the relationship between the input and output is non-linear. Working with non-linearities in the Frequency domain is not straightforward specially when the relationship between the input and output is not trivial. We outline the complete derivation of the Harmonic and Intermodulation distortions from basic principles to a general physical system. For illustration, the procedure is applied to the Single Mode laser diode where the relationship of input to output is non-trivial. The distortions terms are extracted directly from the Laser Diode rate equations and the method is tested by comparison to many results cited in the literature. This methodology is general enough to be applied to the extraction of distortion terms to any desired order in many physical systems in a general and systematic way.

physics.optics↗
arXiv2001

Static and Dynamic Regimes of Arbitrary Gain Compensation Single-Mode Laser Diodes

We report on a methodology for the evaluation of the DC characteristics, small-signal frequency response and large-signal dynamic response of carrier and photon density responses in semiconductor laser diodes. A single mode laser is considered and described with a pair of rate equations containing a novel non-linear gain compensation term depending on a single parameter that can be chosen arbitrarily. This approach can be applied to any type of solid-state laser as long as it is described by a set of rate equations.

physics.optics↗