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Journal of Rare Earths 2022年第3期40卷 473-481,I0005页

作者： Manal benyoussef Halima Zaari Jamal Belhadi Youssef El Amraoui Hamid Ez-Zahraouy Abdelilah Lahmar Mimoun El Marssi Laboratory of Physics of Condensed Matter(LPMC) University of Picardie Jules VerneScientific Pole80039Amiens Cedex 1France Laboratory of Condensed Matter and Indisciplinary Science(LaMCScI) Faculty of ScienceMohammed V UniversityBP 1014RabatMorocco National School of Arts and Crafts Moulay Ismail University50500MeknesMorocco

Na_(0.5)(Bi_(3/4)RE_(1/4))_(0.5)TiO_(3)(RENBT,RE=Nd,Gd,Dy,and Ho)compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave(FP-LAPW)method based on the spin-polarized density functional theory implemented in the WIEN2k *** charge density distribution and Ti K-edge X-ray absorption spectra reveal that the RENBT compositions with high polarization values are accompanied by a higher TiO_(6)distortion,DyNBT,and NdNBT *** effect of the rare-earth elements on the polarization is confirmed experimentally with the collection of the hysteresis *** investigation of the electronic properties of the compounds highlights the emergence of a magnetization owing to the 4f orbital effect of the rare-earth ***,the investigation of the chemical ordering shows a short-range chemical ordering for the pure composition and an increased A-site disorder for dysprosium doped NBT *** increased disorder may speak for increased relaxor properties in the RE doped compositions.

关键词： Density functional theory Sodium bismuth titanate Rare earths A-site ordering Ferroelectric properties Magnetization

An investigation of merging and diverging cars on a multi-lane road using a cellular automation model

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Chinese Physics B 2012年第11期21卷 565-572页

作者： K.Jetto H.Ez-Zahraouy A.benyoussef Laboratoire de Magnétisme et de la Physique des Hautes Energies Universit'e Mohammed V Faculté des Sciences Ecole Hassania des Travaux Publics KM 7 Route DEL JADIDAB.P 8108OasisCasablancaMaroc

In this paper, we have investigated two observed situations in a multi-lane road. The first one concerns a fast merging vehicle. The second situation is related to the case of a fast vehicle leaving the fastest lane back into the slowest lane and targeting a specific way out. We are interested in the relaxation time T, i.e., which is the time that the merging （diverging） vehicle spends before reaching the desired lane. Using analytical treatment and numerical simulations for the NaSch model, we have found two states, namely, the free state in which the merging （diverging） vehicle reaches the desired lane, and the trapped state in which T diverges. We have established phase diagrams for several values of the braking probability. In the second situation, we have shown that diverging from the fast lane targeting a specific way out is not a simple task. Even if the diverging vehicle is in the free phase, two different states can be distinguished. One is the critical state, in which the diverging car can probably reach the desired way out. The other is the safe state, in which the diverging car can surely reach the desired way out. In order to be in the safe state, we have found that the driver of the diverging car must know the critical distance （below which the way out will be out of his reach） in each lane. Furthermore, this critical distance depends on the density of cars, and it follows an exponential law.

关键词： traffic flow merging and diverging area intelligent transportation system cellular au-tomation

The magnetic properties of diluted CoFe_2O_4 nanomaterials

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Chinese Physics B 2012年第4期21卷 513-518页

作者： R.Masrour M.Hamedoun A.benyoussef Laboratory of Materials ProcessesEnvironment and QualityCady Ayyed UniversityNational School of Applied SciencesRoute Sidi Bouzid-BP 6346000 SafiMorocco LMPHE(URAC 12) Facultédes SciencesUniversitéMohamed V-AgdalRabatMorocco Institute for Nanomaterials and Nanotechnologies RabatMAScIRMorocco Academie HassanⅡdes Sciences et Techniques RabatMorocco Academie HassanⅡdes Sciences et Techniques RabatMorocco

The magnetic properties of （Cox Fe1-x）A （Zn1-x Fe1＋x）B O4 are studied using mean-field theory and the probability distribution law to obtain the saturation magnetization, the coercive field, the critical temperature, and the exchange interactions with different values of D （nm） and x. High-temperature series expansions （HTSEs） combined with the Pade approximant are used to calculate the critical temperature of （CoxFe1-x）A（Znl-xFe1＋x）BO4, and the critical exponent associated with magnetic susceptibility is obtained.

关键词： (CoxFe1-x)a(Zn1-xFe1+x)BO4 probability law saturation magnetization coercive field high-temperature series expansions

Auto-correlation Effects on the sp^3-d Exchange Interaction in Cd1-x MnxTe/CdTe Multilayers

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Chinese Physics Letters 2002年第11期19卷 1679-1682页

作者： K. Afif A. benyoussef J. Diouri Laboratoire de Magnétisme Faculté des Sciences B.P. 1014 Rabat Morocco Groupe d'Electronique et de Physique du Solide Faculté des Sciences B.P. 2121 Tetouan Morocco

Band offsets and total energy of Wannier excitons in multilayers are affected by dimensional and auto-correlation effects, and sp3-d coupling is consequently modified. Thus, the calculation of the Zeeman splitting in the quantum wells has to take into account these effects, especially when the mismatch cannot be disregarded. In this work, the theoretical study of these combined effects has been performed for Cd1-xMnxTe/CdTe multilayers embedded by Cd1-yZnyTe as the substrate (or the buffer) on one side and as a cladding layer on the other side. This sample allows us to highlight the role played by the substrate (buffer) and the growth direction on the Zeeman splitting in such multilayers.

关键词： Multilayers

Mean-field and high temperature series expansion calculations of some magnetic properties of Ising and XY antiferromagnetic thin-films

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Chinese Physics B 2012年第8期21卷 487-493页

作者： R.Masrour M.Hamedoun A.benyoussef Laboratory of Materials ProcessesEnvironment and QualityCady Ayyed UniversityNational School of Applied SciencesSafiMorocco LMPHE(URAC-12) Facult'e des SciencesUniversit'e Mohamed V-AgdalRabatMorocco Institute for Nanomaterials and Nanotechnologies MAScIrRabatMorocco Academie Hassan II des Sciences et Techniques RabatMorocco

In this work, the magnetic properties of Ising and XY antiferromagnetic thin-films are investigated each as a function of Neel temperature and thickness for layers （n = 2, 3, 4, 5, 6, and bulk （∞） by means of a mean-field and high temperature series expansion （HTSE） combined with Pade approximant calculations. The scaling law of magnetic susceptibility and magnetization is used to determine the critical exponent γ, veff （mean）, ratio of the critical exponents γ/v, and magnetic properties of Ising and XY antiferromagnetic thin-films for different thickness layers n = 2, 3, 4, 5, 6, and bulk （∞）.

关键词： high-temperature series expansions mean-field theory antiferromagnetic thin film Pade approximant Neel temperature critical exponent

Multilayer transition in a spin-1 Blume Capel model with RKKY interaction and quantum transverse anisotropy

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Chinese Physics B 2011年第1期20卷 609-615页

作者： N.Tahiri H.Ez-Zahraouy A.benyoussef Computational Physics Group LMPHEDepartement de PhysiqueFaculte des SciencesUniversite Mohammed V-AgdalB.P.1014RabatMorocco

Using mean-field theory, we have studied the effect of quantum transverse anisotropies with RKKY interaction on the multi-layer transition and magnetic properties of the spin-1 Blume-Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multilayer magnetic order-disorder transition temperature depends strongly on the value of the transverse anisotropy. The multilayer transition temperature decreases when increasing the transverse anisotropy. Furthermore, there exists a critical quantum transverse anisotropy △xL beyond which the separate transitions occur in the two magnetic layers. The critical transverse anisotropy AxL decreases （increases） on increasing the non-magnetic spacer of thickness M （on increasing the crystal field）, and AxL undergoes oscillations as a function of the Fermi level.

关键词： quantum transverse anisotropy order-disorder lavering transitions. RKKY interaction

Surface Effects on Wannier Excitons in Superlattices:Monte Carlo Simulation

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Chinese Physics Letters 2002年第8期19卷 1164-1167页

作者： K. Afif A. benyoussef J. Diouri Laboratoire de Magnétisme Faculté des Sciences BP 1014 Rabat Morocco Groupe d'Electronique et de Physique du Solide Faculté des Sciences BP 2121 Tetouan Morocco

Using a Monte Carlo quadrature, we calculate by a variational method the binding energy Eb of Wannier excitons in N-period m-CdMnTe/n-CdTe superlattices, including or not including the step discontinuity in the potential barrier at the interface, and with varying N as well as well width. The calculation is performed in the framework of the effective mass approximation for both heavy-hole and light-hole excitons. The degree of exciton localization dependence on these parameters is accurately illustrated.

关键词： Monte Carlo methods

A cellular automata traffic flow modeling of desired speed variability

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Chinese Physics B 2013年第1期22卷 574-577页

作者： K. Bentaleb K. Jetto H. Ez-Zahraouy A. benyoussef Laboratoire de Magnétisme et de Physique des Hautes Energies associéau CNRST (URAC 12) Département de physique B.P. 1014 Facultédes sciences Université Mohammed V Agdal Rabat Morocco Ecole Hassania des Travaux Publics Km 7 Route d'El Jadida BP8108 Oasis Casablanca Morocco Institute of Nanomaterials and Nanotechnologies INANOTECH MACsIR Rabat Morocco Hassan II Academy of Science and Technology Rabat Morocco

The satisfaction rate of desired velocity in the case of a mixture of fast and slow vehicles is studied by using a cellular automaton method. It is found that at low density the satisfaction rate depends on the maximal velocity. However, the behavior of the satisfaction rate as a function of the coefficient of variance is independent of the maximal velocity. This is in good agreement with empirical results obtained by Lipshtat [Phys. Rev. E 79 066110 （2009）]. Furthermore, our numerical result demonstrates that at low density the satisfaction rate takes higher values, whereas the coefficient of variance is close to zero. The coefficient of variance increases with increasing density, while the satisfaction rate decreases to zero. Moreover, we have also shown that, at low density the coefficient variance depends strongly on the probability of overtaking.

关键词： traffic celluar automata satisfaction coefficient desired speed

Magnetic properties of Mn-doped GaN with defects:ab-initio calculations

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Chinese Physics B 2011年第8期20卷 297-303页

作者： E.Salmani A.benyoussef H.Ez-Zahraouy E.H.Saidi LMPHE Departement de PhysiqueFacult'e des SciencesUniversit'e Mohammed V-AgdalRabatMorocco LPHE Departement de PhysiqueFacult'e des SciencesUniversit'e Mohammed V-AgdalRabatMorocco

According to first-principles density functional calculations, we have investigated the magnetic properties of Mn- doped GaN with defects, Ga1-x-yVGxMny N1-z-tVNzOt with Mn substituted at Ga sites, nitrogen vacancies VN, gallium vacancies VG and oxygen substituted at nitrogen sites. The magnetic interaction in Mn-doped GaN favours the ferromagnetic coupling via the double exchange mechanism. The ground state is found to be well described by a model based on a Mn3＋-d5 in a high spin state coupled via a double exchange to a partially delocalized hole accommodated in the 2p states of neighbouring nitrogen ions. The effect of defects on ferromagnetic coupling is investigated. It is found that in the presence of donor defects, such as oxygen substituted at nitrogen sites, nitrogen vacancy antiferromagnetic interactions appear, while in the case of Ga vacancies, the interactions remain ferromagnetic; in the case of acceptor defects like Mg and Zn codoping, ferromagnetism is stabilized. The formation energies of these defects are computed. Furthermore, the half-metallic behaviours appear in some studied compounds.

关键词： diluted magnetic semiconductor GaN:Mn defects ab-initio magnetic properties

First-principles prediction of the magnetism of 4f rare-earth-metal-doped wurtzite zinc oxide

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Journal of Rare Earths 2014年第8期32卷 715-721页

作者： A.G.El Hachimi H.Zaari A.benyoussef M.El Yadari A.El Kenz Laboratoire de Magnétisme et Physique des Hautes Energies LMPHE (URAC 12) Département de Physique B.P.1014 Faculté des SciencesUniversité Mohammed V-Agdal Institut of Nanomaterials and Nanotechnology Hassan II Academy of Science and Technology Department of Science Moulay Ismail University Faculté Polydisciplinaire

Electronic structure and magnetic properties of wurtzite ZnO semiconductor doped with rare earth （RE=La, Ce, Pr, Pm, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb） atoms were studied using spin-polarized density functional theory based on the full-potential linear augmented plane wave （FP-LAPW） method as implemented in the Wien2k code. In this approach the generalized gradient approximation （GGA） was used for the exchange-correlation （XC） potential. Our results showed that the substitution of RE ions in ZnO induced spins polarized localized states in the band gap. Moreover, the studied DMSs compounds retained half metallicity at dopant concentration x=0.625%for most of the studied elements, with 100%spin polarization at the Fermi level （EF）. The total magnetic moments of these compounds existed due to RE 4f states present at EF, while small induced magnetic moments existed on other non-magnetic atoms as well. Finally, the energy difference between far and near configurations was investigated. It was found that the room temperature ferromagnetism was possible for RE-doped ZnO at near configuration. Since the RE-RE separation was long enough （far configuration） for magnetic coupling, the system became paramagnetic or antiferromagnetic ground state.

关键词： ZnO rare earths ferromagnetism DMS electronic structure magnetic properties half-metallic RE-doped ZnO FP-LAPW method density functional theory