Volume 6, article 1
F. Hanke and M. Azzouz
In this work, we used a periodic lattice potential in order to model the infrared optical data of the high-temperature superconductor La2−xSrxCuO4. This potential consists of a two-dimensional array of double-well potentials, which simulate the CuO2 layers. It is obtained by assembling Cu-O-Cu units rather than Cu and O single atoms in the tight-binding approach. A gap separating two energy bands can be obtained and is used to fit the infrared (IR) optical gap of this cuprate. We derived the dielectric function and showed that in the classical limit it reduces to the one consisting of a Drude term plus a number of lorentz components, equivalent to the dielectric function used empirically by several authors in their fits of the reflectivity. By refitting available reflectance data, we deduced a simple law for the doping dependence of the optical gap in La2−xSrxCuO4. In the present study, we argue that the optical gap is distinct from the pseudogap or the two-magnon gap, because it characterizes La2−xSrxCuO4 for all doping regimes.
Keywords : Evanescent wave, Resonant modes, Far-field Detection, Diagnostic of the metal/dielectric Interface.
Department of Physics and Astronomy, Laurentian University,935 Ramsey Lake Road, Sudbury, Ontario, P3E 2C6 Canada
_________________________
Volume 6, article 2
Magnons plane by plane contribution to super-lattice magnetic properties
A. Fahmi and A. Qachaou
The paper presents a contribution to the study of super-lattice magnetic properties in the linear spin-wave theory framework. The super-lattice is represented by a Heisenberg ferromagnet with N atomic planes. The excitation spectrum and the magnetization are calculated using Green’s functions method. Their expressions are obtained analytically for N=3,5 and 10 atomic planes. The effects of both surface anisotropy and dipolar interaction are studied numerically.
Laboratoire de Physique de la matière condensée, Faculté des sciences, Kénitra, Morocco.
_________________________
Volume 6, article 3
Magnetic studies of amorphous Fe-Dy-B ribbons
F. Annouar(a), K. Roky(b,c), A. El
moussaoui(c), L. Driouch(a),
M. Abid(a), and H. Lassri(a)
We have studied the magnetization of melt spun amorphous Fe80−xDyxB20 alloys with 0 ≤ x ≤ 7.5 under magnetic fields up to 6T, and have analyzed the results at 4.2 K on the basis of the random magnetic anisotropy model. Exchange constant and local random anisotropy KL were evaluated. Using the Sarkis´s model, the local anisotropies per atom are found to be 1.75 107 and 4 107 erg/cm3 for Fe and Dy, respectively.
Keywords: Amorphous ribbons; Magnetization; Local random anisotropy.
(a)Laboratoire de
Physique des Matériaux et de Micro-electronique,Faculté des
Sciences Ain Chok, Université Hassan II, Maarif, B.P. 5366,
Casablanca, Morocco.
(b)Département de Physique, Facuté des Sciences et Techniques de
Tanger, Morocco.
(c)Département de Physique, Faculté des Sciences de Tetouan,
Morocco.
_________________________
Volume 6, article 4
Ionizing
Radiation Effect on the Electrical Properties of
Metal/ultra-thin
Oxide/Semiconductor Structures
Y. Khlifi1,
K. Kassmi1*,
A. Aziz1,
F. Olivié2
G. Sarrabayrouse2,
A. Martinez2
This paper deals with the effects of X-ray radiation (7 Mrad (Si) dose) on the electrical properties of Metal/Oxide/Semiconductor (MOS) structures with ultra thin oxide layer (45 Å to 80 Å), P-type semiconductor (Si), and a chromium gate.
These effects are investigated on the Fowler-Nordheim (FN) conduction and the excess current when the MOS structure is biased with a positive gate voltage (Vg>0) (inversion regime); and on the breakdown field when electrons are injected from the metal (accumulation regime, Vg<0).
By using the theoretical conduction model developed in a previous paper [1], we have found that the FN conduction parameters improve after radiation. We have interpreted this result, by modelling the excess current before and after radiation, by improving the conduction parameters of defects localized in the oxide layer. Thus the defect barrier was increased by 6.5% while the effective area decreased by 68%.
The analysis of the radiation effect on breakdown distribution shows the degradation of the breakdown field after radiation. These results suggest that the ionising radiation can be involved in the formation of another type of defects in the oxide layer that can lead to the breakdown phenomenon but cannot impact the FN conduction mechanism.
(1) Université Mohamed Premier, Faculté des Sciences,
Dépt de Physique, (L.E.A.A), Route Sidi Maafa BP 524,
Oujda, Morocco.
(2) Laboratoire d’Analyse et d’Architecture des Systèmes
(LAAS-CNRS), 7 Avenue du Colonel Roche, Toulouse 31077,
France.
_________________________
Volume 6, article 5
Modelling of Collision in the Plasma Sheath and the Cathode Erosion of Electrical Arc
B.Zine1,
D.Saifaoui1,
A.Dezairi2,
T.Es-sabbar1,
A.Boumhali1,2,
M.ElMouden1
In order to improve many industrial applications of the plasma sheath and the cathode erosion of electrical arc, the prime objective of this paper is to treat the modelling and simulation of the effects of ions collisionality on the plasma sheath and to determine the collisional dependence of the sheath width and the ion impact energy on the wall using the Runge-Kutta Routrine on the presence or the absence of the term source in the continuity equation . Then , to explain the dependence of the measured erosion rate of the cathode by considering the cathode spot heat balance equation coupled with equation obtained from the sheath and taking into account the physical phenomena such as ion and electron fluxes, radiation, thermal conductivity and evaporation.
Keywords: : sheath, modelling collision, cathode erosion, impact energy, sheath width , spot.
1-Laboratoire de Physique Théorique –
Groupe de Physique des Plasmas Faculté des
Sciences Ain Chock BP 5366 Maarif Casablanca
Morocco.
2- Laboratoire de la Matière Condensée-
Faculté des Sciences Ben M’sik Casablanca
Morocco.
_________________________
Volume 6, article 6
Potential of a wire bent into a circular shape Application to Saturn’s Rings
Najid N-E Jammari M-K and Zegoumou M.
In this article, we develop the calculation of the potential generated by a homogeneous wire bent into a circular shape [1]. In a second time we develop a new method of perturbation. It gives an expression of the potential in terms of R, the radius of the circle. The potential is expressed as a sum of the Newtonian and a small term. The former will be considered as a perturbation. We give the orbits of a test particle in accordance with the initial conditions. Precession of perihelia or chaotic cases is proved [2]. In an accurate way, we must use a juxtaposition of such circular wires, in order to built a two dimensional disc.
Keywords: Potential-Legender Polynoms-Rings-Saturn.
Groupe Astronomie Astrophysique
Laboratoire de Physique Théorique
Université Hassan II Ain Chock Faculté des
Sciences
Ain Chock BP 5366 Maârif Casablanca,
Morocco.
najid.nour_eddine@caramail.com
_________________________
Volume 6, article 7
Modelling and
simulation
of dusty plasma sheath
M. Eddahby1,
M. Samir1,
A.Dezairi1,
D.Saifaoui2,
Elhaitami1,
R.Moulatif
The aim of this paper is to study the behaviour of sheath structure in dusty plasma with collisions, and simulation of the effects collisionality on the plasma sheath using the Runge-Kutta routine. Exact numerical solutions of the model are used to determine the collisional dependence of the sheath width and the ion impact energy at the wall.
Keywords: sheath, dusty plasmas, sheath width, collision parameter, impact energy
PACS number.52.65.+z
1 Laboratoire de Physique de la Matière
Condensée, Faculté des Sciences Ben M’sik,
B.P. 7955, Casablanca,
Morocco
2 Laboratoire de Physique Théorique,
Groupe de Physique des Plasmas, Faculté
des Sciences Ain Chock, BP 5366.Maarif,
Casablanca
Morocco
_________________________
Volume 6, article 8
Relaxation and transport mechanisms in (Pb.79La.21Ti.95)O3 ceramic
K. Limame, M. Kellati, S. Sayouri
Variations of the dielectric constant and the relaxation time of La- doped PbTiO3 ceramic, as functions of frequency, are studied using the well- known model of Debye. The conductivity of the material is also studied and the variation of the activation energy as function of frequency is discussed.
LPTA, Département de Physique, B. P. 1796, Fès-Atlas, Morocco.
_________________________
Volume 6, article 9
Bacteriological study by bacterial counting on the level of the interstitial sediments of Sebou River
Raja Guemmouh1, Khadija Essafi1& Nezha Aouad2
The Sebou River constitutes one of the most important resources of Morocco, receives in his middle section of the daily dismissals of sloppy waters from the city of Fès (a city of Morocco). The present survey analyses the impact to the downstream of these dismissals on the quality of these interstitial waters and on the sediments. The bacterial numbering is used for the assessment of the bacterial biomass. This one shows a big spatio-temporal variability, especially as she is in narrow relation with the nature of the substratum. Within this aquiferous fluvial, the microbial activity and the bacterial numbering are bound to abundance and the distribution of the thin sediments and very ends. The temporal dynamics of the hydrologic factor is determining in the phenomena of accumulation, of retention and the dynamics of the bio-movie.
1
Laboratoire d’Hydrobiologie et Ecologie
générale. Faculté des Sciences Dhar El
Mehraz B.P.1796-atlas Fès,
Morocco.
2
Laboratoire d’Ecologie. Université Hassan
II, Faculté des Sciences, Aïn Choq.
Casablanca,
Morocco.
_________________________
Volume 6, article 10
On- and Off-ramps
Generating 1/f
Noise
in Traffic Flow
K. Nassab1,2, R. Barlovic1, M. Schreckenberg1, and S. Ouaskit2
A simple model of a motorway junction consisting of two connected periodic roads is presented; each of them is connected to the other by on- and off-ramps. This constitutes a detailed structure for the region of on- and off-ramps, which is a new aspect of this paper and a useful step towards a more realistic modelling of the vehicular dynamics near the ramps. The traffic flow through the ramps has an effect on the capacity of the main roads. This effect is identified by the formation of the so-called ”plateau” in the fundamental diagram. The value increase of one of the probabilities pin and pout decreases the value of the indicated plateau. Here pin is the probability to enter the main road through the on-ramp and pout denotes the probability to exit the main road through the off-ramp. The first important feature in the simulated system is the symmetry between the connected main roads. This symmetry does not depend on the variation of the difference between the probabilities pin and pout. The other most outstanding feature is the existence of correlations between the connected main roads, which can be traced back to the lane change of vehicles in the ramp regions. These correlations are characterized by the occurrence of 1/fα fluctuations in the global traffic flow of a chosen main road of the simulated system.
(1)
Theoretische Physik Fakultät 4,
Universität Duisburg-Essen, D-47048
Duisburg, Germany.
(2) Laboratoire de Physique de la Mati`ere
Condensée, Facult´e des Sciences Ben
M’sik, BP 7955 Ben M’sik,
Casablanca, Morocco
_________________________
Volume 6, article 11
Stuctural And
Magnetic Characterization
Of CoxZn1-x/Cu
Multilayers Obtained by Electrodeposition
T.
Elbahraouia,
H. Errahmania,
A. Berrada*
a, A.
Diniab,
G. Schmerberb
F. Cherkaoui ElMourslic,
F. Hajjic,
H. Lassrid,
H. Ouahmanee
We present the experimental results of (CoxZn1-x/Cu)n multilayers (3<x<10) grown using the electrochemical dual bath method. The X-ray diffraction patterns have shown that the CoZn structural lattice parameters are close to those of the monoclinic CoZn13 compound.
We have developed an analytical model in the X-ray kinematical theory adapted to the electrodeposited (CoxZn1-x/Cu) multilayers. We have shown that the model can give interesting structural information about the multilayer components, and reproduces the position of the satellite peaks around the main diffraction peak. Thus we have deduced the multilayer period and performed comparison between experimental results and the analytical model. The magnetic properties at room temperature reveal both superparamagnetic and ferromagnetic features. The inclusion of Zn into the magnetic layer and the existence of CoZnCu based alloy at the interfacial regions explain the magnetic properties. The magnetoresistance (MR) loop displays a broad , rounded maximum and the saturation is not observed even at high applied fields. The MR(H) behaviour and its small ratio can be attributed to interfacial effects
Keywords: (CoxZn1-x/Cu)n; multilayers; electrodeposition; magnetoresistance; superparamagnetism;
a
Laboratoire de Physique des Matériaux,
Faculté des Sciences , BP1014, Rabat,
Morocco.
b
IPCMS-GEMM,ULP,UMR 46 CNRS, 23rue du loess
,67037 Strasbourg, France.
c
LECA, Département de Chimie Faculté des
Sciences, BP1014 ,Rabat, Morocco.
d
L.P.M, Département de Physique , Faculté
des Sciences, Ain Chock B.P. 5356,
Casablanca , Morocco.
e
Faculté des Sciences et Techniques,
Département de Physique, Errachidia,
Morocco.
_________________________
Volume 6, article 12
Magnetization study of Ni/Ag multilayers
R. Elkabil1,
K. Benkirane1,
H. Lassri2,
A. Hamdoun1,
M. Lassri2
and R. Krishnan3
The magnetic properties of Ni/Ag multilayers, prepared by evaporation in ultrahigh vacuum under controlled conditions, have been systematically studied by magnetic measurements. A spin-wave theory has been used to explain the temperature dependence of the magnetization and the approximate values for the bulk exchange interaction Jb and surface exchange interaction JS for various Ni layer thicknesses have been obtained.
Keywords: Ni/Ag multilayers; Magnetization; Exchange interactions.
1
Laboratoire de traitement d’information,
Faculté des Sciences Ben’Msik
Sidi-Othmane, B.P. 7955 - Sidi-Othmane,
Casablanca, Morocco.
2
Département de Physique, Faculté des
Sciences Ain Chock, Université Hassan II,
B.P. 5366 Mâarif, Route d’El Jadida, km-8,
Casablanca, Morocco.
3
Laboratoire de Magnétisme et d’Optique,
URA 1531, 45 Avenue des Etats Unis, 78035
Versailles Cedex, France.
_________________________
Volume 6, article 13
Alloying effects on the magnons properties in [Ni-Fe/Cu] superlattices
A. Fahmi , A. Qachaou* and M. Elharfaoui
We analysed the properties of the magnetic excitation for the simple [Fe/Cu] and [Ni/Cu] super-lattices as well as for the [Ni1-xFex/Cu] alloy by the linear spin waves method. The obtained excitation spectra and the magnetization behaviours are in agreement with those we have already obtained for [Co/Cu][1,2]. The introduction of the Iron increases the magnons energy, the gap, magnetization by spin and the critical temperature in the studied alloy.
Keywords: Alloy, multilayer, spin waves, excitation spectra, magnetization, Green’s function, and anisotropy.
Laboratoire de physique de la matière
condensée, Département de physique,
Faculté des Sciences, B. P. 133-14000,
Kenitra, Morocco,
e-mail :ahqachaou@yahoo.com
_________________________
Volume 6, article 14
Dielectric and relaxation studies in hydrothermal processed PLZT ceramics
T.
Lamcharfi1,2,
S. Sayouri1,
N.S. Echatoui1,2,
E. Ech-chamikh3,
A.Outzourhit3,
L.Hajji3,
D.Mezzane3
(Pb1-yLay)(Zr0.52Ti0.48)O3 (PLZTy) powders were prepared using hydrothermal process and their structural and dielectric properties investigated. Increasing La content is shown to enhance crystallization of the raw samples and to transform the average symmetry to tetragonal one in the calcined ones. Two anomalies are observed on the real part of the permittivity on the sample with y = 0.03, at a relatively high temperatures (~ 180 °C, ~ 260 °C). The latter was interpreted as a transition from ferroelectric-rhombohedral phase to ferroelectric-quadratic phase. A quadratic law in temperature was used to study the temperature dependence of the dielectric constant of the samples showing the relaxation phenomenon and values of the fitting parameters such as the diffuseness parameter were calculated and discussed.
Keywords: PLZT; Dielectric anomalies; Relaxation, MPB; Diffuseness parameter
1
LPTA, Dépt Physique, Faculté des
Sciences-DM, B.P. 1796, Fès-Atlas,
Morocco.
2
LSSC Dépt Génie Electrique, FST, Route
d’Immouzer, Fès, Morocco.
3
LPSCM, Faculté des Sciences Semlalia, B.P.
2390, Marrakech, Morocco.
4
LESEO dépt physique, FST Guiliz Marrakech,
Morocco.
_________________________
Volume 6, article 15
Study of surface
diffusion by Langevin
Dynamics simulation
S. Zayzoune, M. Mazroui and Y. Boughaleb
We investigate the dynamic properties of Brownian interacting particles subject to a two-dimensional periodic potential. By employing the Langevin dynamics simulation, we calculate the collective diffusion coefficient in different situations corresponding to different densities. On the other hand, our numerical studies show that the collective diffusion coefficient depends not only on the shape of adsorbed potential but also on the coupling between particles.
Keywords: Commensurability effects; Computer simulations; Surface diffusion, Brownian motion.
Université Hassan II. Faculté des Sciences Ben M’sik. Laboratoire de Physique de la Matière Condensée, B.P. 7955, Casablanca Morroco
_________________________
Volume 6, article 16
Atomic scale
simulation of epitaxial growth:
Cases of GaAs/GaAs
and CdTe/GaAs
M. Sahlaoui1,
N. Fazouan1,
M. Sajieddine1,
M. Djafari. Rouhani2,3,
A. Esteve3
We present a kinetic Monte Carlo model describing the growth by molecular beam epitaxy (MBE) of semiconductor compounds and including a local photoemission model with reflection high-energy electron diffraction (RHEED) intensity for comparison. We investigate the cases of both homoepitaxial and heteroepitaxial growth. The valence force field approximation is used for the strain energy calculations in mismatched thin films In homoepitaxial growth of GaAs, we have study the variations of photoemission current and RHEED intensity and examined the GaAs morphology. In high lattice mismatch heteroepitaxial growth (CdTe/GaAs), we have shown the formation of grooves corresponding to (111) facets, precursor to the formation of misfit defects.
Keywords: Simulation; Interface structure, Photoemission current; Reflection high-energy electron diffraction; crystal defects.
(1)
Laboratoire de Physique des Matériaux,
Faculté des Sciences et Techniques, B.P
523, 23000 Beni Mellal, Morocco.
(2) Laboratoire de Physique des Solides,
Université Paul Sabatier, 118 Route de
Narbonne, 31062 Toulouse Cedex, France.
(3) Laboratoire d’Analyse et
d’Architecture des Systèmes, 7 avenue du
Colonel Roche, 31077 Toulouse Cedex,
France.
_________________________
Volume 6, article 17
Reponses Of A
Metallic Bubble: A Self-Consistent
Calculation Including
Correlation And Exchange Effects
A. Semlalia, A. Doufareb J. Gadhib and B. Labanib
The Van der Waals energy of molecules interacting with metallic bubbles is determined from spherical-tensor theory by using the response field susceptibility of the spherical bubble. The correlation and exchange effects of the electron response inside the metal are included by using the local density approximation (LDA). The dependence of the Van der Waals energy on the first Euler angle is manifestation of the anisotropy of the interaction. In order to illustrate the non-locality and the correlation and exchange effects as well as the importance of the spherical bubble curvature and anisotropy of the interaction on the potential magnitudes, we present numerical results for typical systems (HF,HCl) molecules on (Ag,Al) surfaces.
Keywords: metallic bubble, Van der Waals energy, correlation and exchange effect.
a-
Département de physique, Faculté des
Sciences. Université Chouaib Doukkali,
Route de Ben Maâchou, 24000 El Jadida,
Morocco.
b- Département de physique, Faculté des
Sciences Semlalia, Université Cadi Ayyad,
BP 2390, Marrakech, Morocco.
_________________________
Volume 6, article 18
Evaluation Of The Damage In The Stainless Steel Coatings By Residual Stress Measurement
S.
Laaroussi*, B.Boubeker*, M. Talea*, M.
Idiri*,
A. Abouzaid*, P.O. Renault**, Ph.
Goudeau**
Thin solids films of 304L stainless steel are prepared by the ion beam sputtering technique. The obtained films present a debonding phenomenon and a high compressive stress state. The critical stress value causing the debonding phenomenon is determined using atomic force microscopy (AFM). By ion beam assisted deposition (IBAD) process during the films elaboration, we observe a stress relaxation. This effect is measured using the X-ray diffraction method sin2Ψ.
Keywords: Stainless steel films; Residual stresses; X-ray diffraction; Atomic force microscopy.
*Université Hassan II – Mohamedia, Faculté
des Sciences Ben M’Sik, Département de
Physique,
UFR: Milieux Denses et Matériaux, B.P 7955
Sidi Othman , Casablanca, Morocco
**Université de Poitiers, UFR Sciences,
S.P.2M.I, Laboratoire de Métallurgie
Physique,
URA 131 du CNRS, Bd 3, Téléport 2, BP.
179, 86960 Futuroscope cedex, France
_________________________
Volume 6, article 19
Determination of the
Structure and Thermodynamics of Square
Well Potential From the Tail
of the Direct Correlation Function
F.Smain and F.Ould-Kaddour
Following Stell, one can determine the pair correlation function h(r) of the hard sphere fluid for all distance r by specifying only the tail of the direct correlation function c(r) at separation greater than the hard core diameter σ . More recently, Katsov and Weeks extended Stell ideas to describe the structure of continuous fluids containing repulsive and attractive parts like Lennard-Jones and Yukawa fluids. In this paper, we extend these ideas to determine the structure and thermodynamics of square well potential from the tail of the direct correlation function. This potential is used essentially to model complex systems like polymers and colloids. We use the Martinov-Sarkisov bridge functions in the closure relation. An efficient numerical algorithm is used based on Labick procedure. We give results for the structure and thermodynamics at different values of the width of the square well potential, and at different thermodynamical states.
Keywords: square well potential, structure, thermodynamics, and correlation functions.
Laboratoire de Physique Théorique, Département de Physique.- Faculté des sciences- Université Aboubakr BELKAÏD. B. P 119 Tlemcen (13000) Algeria
_________________________
Volume 6, article 20
Phase-field modelling of dendritic growth behaviour towards the cooling / heating of pure nickel
B. Kaoui1, M. Noureddine1, R. Nassif 1.2 and Y. Boughaleb1
We are interested in modelling the dendritic growth occurring during the solidification process of a pure material and especially to see the effect of the cooling / heating on the growth behaviour of this dendrite.
For this purpose we use a phase-field model. The obtained partial differential equations are solved numerically by a finite difference method. In order to appreciate the shape of the resulting dendrites we expose some figures obtained from simulations in 2D.
Keywords: Simulation, dendritic growth, phase-field models, finite difference method.
1Laboratoire de Physique de la Matiére
Condensée, Faculté des Sciences Ben M’Sik.
Casablanca / Morocco.
2Laboratoire de Physique de la Matiére
Condensée, Faculté des Sciences El-Jadida.
El-Jadida / Morocco.
Copyright © The Moroccan Statistical Physical Society. [mjcm@fsr.ac.ma]. Last modification : December 2009.
ISSN : 1114-2073