Volume 10, article 1

Magnetization and ordering temperature
of films and multilayers

L. Bahmad, A. Benyoussef, A. El Kenz, H. Ez-Zahraouy and M. Loulidi

We investigate, in this paper, a number of magnetic properties of single and multilayer thin film systems within the Ising model by application of mean field, finite cluster approximations as well as by Monte Carlo simulations. The magnetization profiles and the magnetic ordering temperature are calculated for different magnetic systems. The influence of corrugation and disorder at the surface, on the critical behavior of ferromagnetic Ising film is also studied. It is found that the critical surface exponent of the magnetization follows closely the one of a perfect surface, in the two cases: corrugated surface and random equiprobable coupling surface. However, in the case of flat surface with random interactions the surface critical exponent depends on the concentration of the strong interaction, while such critical exponent is independent on the concentration. Moreover, in the case of corrugated surface, the effective exponent for a given layer, is a function of the number of steps at the surface. The probability of a magnetic ground state is larger for low spatial dimensionality of an extended system, or lower for local symmetry of a given site in the atomic lattice. Consequently, the magnetic properties are usually more pronounced at the surface of a bulk magnet as compared to the bulk interior. The phase diagram and the characteristic behaviors of the surface magnetization, are investigated for amorphous or cristalline surfaces. Indeed, the size effects become more relevant at low temperature depending on film thickness.

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Laboratoire de Magnétisme et Physique des Hautes Energies Département  de Physique, Faculté des Sciences Avenue Ibn Batouta, B.P 1014  Rabat Morocco

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Volume 10, article 2

Static and Vibrational Properties of Alkali Metals

Aditya M. Vora

The computations of the static and vibrational properties of five alkali metals viz. Li, Na, K, Rb and Cs to second order in local model potential is discussed in terms of real-space sum of Born von Karman central force constants.  The exchange and correlation functions due to Hartree (H) and Ichimaru-Utsumi (IU) are used to investigate influence of screening effects.  Results for the lattice constants i.e.C11, C12, C44, C12-C44, (n) and bulk modulus (n) obtained using the Hartree (H) local field correction function has higher values in comparison with the results obtained for the same properties using Ichimaru-Utsumi (IU) local field correction function. The results for the Shear modulus(C'), deviation from Cauchy’s relation, Poisson’s ratio s, Young modulus Y, propagation velocity of elastic waves, phonon dispersion curves (PDC) and degree of anisotropy A are highly appreciable for the alkali metals.  The phonon frequencies of alkali metals in the longitudinal branch are more sensitive to the exchange and correlation effects in comparison with the transverse branches. The phonon dispersion curves (PDC) of pure alkalis are found in qualitative agreement with the available experimental data. While, the frequencies in the longitudinal branch are suppressed due to IU-screening function than the frequencies due to static H-screening function.

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Keywords : Pseudopotential, alkali metals, static and vibrational properties.
PACS:  62.30.+d, 63.20.-e, 63.20.Dj

Parmeshwari 165, Vijaynagar Area, Hospital Road, Bhuj – Kutch, 370 001, Gujarat, INDIA.
 E-mail: voraam@yahoo.com.

 

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Volume 10, article 3

Superconducting State Parameters of Ternary Metallic Glasses

Aditya M. Vora

The screening dependence investigations of the superconducting state parameters (SSP) viz. electron-phonon coupling strength l, Coulomb pseudopotential µ*, transition temperature Tc , isotope effect exponent a and effective interaction strength NoV of some ternary metallic glasses viz. Ti50Be34Zr10, (Mo0.6Ru0.4)78B22, (Mo0.6Ru0.4)80B20, (Mo0.4Ru0.6)80P20, (Mo0.6Ru0.4)70Si30, (Mo0.6Ru0.4)84B16, (Mo0.6Ru0.4)72Si28, (Mo0.6Ru0.4)86B14, (Mo0.6Ru0.4)76Si24, (Mo0.6Ru0.4)78Si22, (Mo0.6Ru0.4)80Si20, (Mo0.6Ru0.4)82Si18 and (Mo0.6Ru0.4)80P20 have been reported for the first time using Ashcroft’s empty core (EMC) model potential.  Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. It is observed that the electron-phonon coupling strength l and the transition temperature Tc are quite sensitive to the selection of the local field correction functions, whereas the Coulomb pseudopotential µ*, isotope effect exponent aand effective interaction strength NoV show weak dependences on the local field correction functions. The Tc obtained from H-local field correction function are found an excellent agreement with available experimental data. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirms the superconducting phase in the ternary metallic glasses.

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Keywords: Pseudopotential; superconducting state parameters; ternary metallic glasses.
PACS Number(s): 61.43.Dq; 71.15.Dx; 74.20.-z; 74.70.Ad

Parmeshwari 165, Vijaynagar Area, Hospital Road, Bhuj – Kutch, 370 001, Gujarat, India

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Volume 10, article 4

Surface phase diagram of the Ising model with modified surface-bulk coupling

T. Lahcini and N. Benayad

The phase diagram of the three-dimensional Ising system with intrasurface Js and surface-bulk J^ interactions modified with respect to the bulk exchange interaction Js is studied by the use of an effective field method within the framework of a single-site cluster theory. In this investigation, the new parameter J^ strongly affects the phase diagram obtained recently in the case J^=Js. Indeed, our calculations reveal some qualitatively interesting features for the surface when the bulk is ordered or disordered. Surface magnetisations are also investigated for different values of the ratio R=Js /JB

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Keywords:  Surface magnetism; Surface phase diagram; Surface-bulk coupling; Effective field theory
PACS: 75.10.Hk; 75.50.Ee; 75.70.Rf

Groupe de Mécanique Statistique, Laboratoire de Physique Théorique, Faculté des Sciences, Université Hassan II-Aïn Chock, B.P. 5366 Maarif, Casablanca 20100, Morocco

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Volume 10, article 5

Phase diagrams of nanoparticles of diluted magnetic semiconductors

M. Hamedoun (a,*), R. Masrour (a), K. Bouslykhane (a), A. Hourmatallah (a, b),N. Benzakour (a) and A. Benyoussef(c)

The magnetic properties of diluted magnetic semi conductors (DMS)Cd1-xMnxTe are investigated. Using the mean field theory, we have evaluated the critical temperature from the nearest neighbour interactions and the energy exchange for the different diameter of the Cd0.5Mn0.5Te nanoparticle. The critical exponents are obtained. The magnetic phase diagrams (Tc versus dilution ) have been determined by the High-temperature series expansions. The critical exponents associated with the magnetic susceptibility (g) and correlation lengths (v) are deduced

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Keywords: : Diluted magnetic semi conductors; critical temperature; nanoparticle; critical exponents; High-temperature series expansions; Padé approximants, Phase diagram.

a: Laboratoire de Physique du Solide, Université Sidi Mohammed Ben Abdellah, Faculté des sciences, BP 1796, Fes, Morocco.
 b: Equipe de Physique du Solide, Ecole Normale Supérieure, BP 5206, Bensouda, Fes, Morocco.
c: LMPHE,Faculté des Sciences, Université Mohamed V, Rabat, Morocco.
 * Corresponding author: e-mail: hamedoun@hotmail.com

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Volume 10, article 6

Global Existence and Uniqueness of a Field Modelling the Thermal State of Three-dimensional Superconductor (1≤ N ≤ 3)

M. El Khomssi a, S. Saoud b, M. Fikri c

In this paper, we will study the global existence of a thermic field modelling the physical state of a three - dimensional superconductor. The superconductor is considered as a widely bounded regular field, with the usual physical data.

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Keywords: , existence, monotonous operator, supraconductors.

a ) khomsixmath@yahoo.fr, UFR MDA, Fés 3001, Morocco.
 b) mat-rahas@hotmail.com, Calcul Scientique & Sciences de l'ingénieur.
c ) majdakri@yahoo.fr; Calcul Scientique & Sciences de l'ingénieur

Copyright C The Moroccan Statistical Physical Society. [mjcm@fsr.ac.ma]. Last modification : December 2010. 

ISSN : 1114-2073