Browsing by Author "Blizak, Salah"

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AB initio dft investigations of magnetic properties of 3d transition metal alloy films
(2013) Blizak, Salah
The objective of this work is to employ spin-polarized density functional theory (SDFT) calculations for the exploration of ultrathin magnetic lms with large magnetic moments and a strong perpendicular anisotropy. Ultrathin monolayer lms of Fe1..xCox (with x = 0, 0:25, 0:5, 0:75 and 1) on Rh(001) were addressed to study their magnetic properties using the all-electron full-potential linearized augmented plane wave (FLAPW) method in lm geometry. We studied the magnetic order of these lms including relaxations of the topmost layers. Fe1..xCox monolayer lms were found to be ferromagnetic (FM) in a broad range of Co content x with a maximum magnetic moment of 2:8 B and of an out-of-plane magnetocrystalline anisotropy of 0:25 meV per magnetic atom at x = 0:5. The SDFT results were mapped onto a classical Heisenberg model, demonstrating FM Fe-Co and Co-Co coupling, while the Fe-Fe interaction is antiferromagnetic (AFM) on Rh(001). The ordering temperature was estimated to be well above room temperature (482 K). Using SDFT calculations, we have studied the magnetic states including collinear and noncollinear magnetic coupling in Fe1..xCox ultrathin lms on Rh(001) substrate. We found for 7 layes of Rh spacer an interlayer exchange coupling (IEC) with absolute values of 3:4 and 2:9 meV per 3d atom corresponding to the two magnetic lms Co/Rh/Co and FeCo/Rh/Co, respectively. These lms show a very large IEC compared to that obtained for Fe/Ag/Fe or Fe/Au/Fe lms, which is IEC is one order of magnitude smaller. We found also that the IEC oscillates with increasing Rh spacer thickness, i.e. the Rh spacers mediate an interlayer coupling which couples the magnetizations either ferromagnetically or antiferromagnetically depending on the spacer thickness. Our calculations give an antiferromagnetic (AFM) coupling for 5 layers of Rh spacer and a ferromagnetic (FM) one for 7 layers, as has been experimentally detected for thicker magnetic lms. The exchange coupling energy including spin orbit coupling was calculated for the nFeCo/5Rh/Co lms in the framework of of the constrained SDFT. A strong perpendicular anisotropy of 0:15 meV per 3d atom has been found for the 2FeCo/5Rh/Co lm while the single FeCo monolayer system FeCo/5Rh/Co preferred an in-plane magnetic anisotropy. This result suggests that the competition between IEC and magnetic anisotropy of coupled lms may result in noncollinear ordering. The results of the constrained SDFT are mapped onto the bilinear-biquadratic exchange coupling model of the Hamiltonian including the uniaxial anisotropy term. We found a values of 3:55 and 0:62 meV per 3d atom for the bilinear and biquadratic coupling constants respectively Fonctionnelles densité Density functionals
The effect of atmospheric optical phenomena photographed by students on learning motivation
(2018) Blizak, Meriem Djanette; Remli, S.; Blizak, Salah
The atmospheric optical phenomena (mirages, rainbows, halos, blue sky, sunset …) that we can observe in everyday life are very interesting for stimulating the students’ curiosity. This study aimed to investigate the effect of atmospheric optical phenomena photographed by university students’ on their learning motivation in geometrical optics (GO). To achieve the aim of the study, an available sample of the study composed of (200) students from the biology department of Boumerdes University, Algeria, was used. The subjects were randomly distributed into two groups: (165) of them in the experimental group and (35) in the control group. We have asked every student in the experimental group to use their smartphone or tablet to taking photos of an atmospheric optical phenomena and giving a physical explain. According to the motivation post and pres test, there were statistical significant differences in learning motivation in the favor of the experimental group
Gamma radiation effect on a murataite ceramic doped with Sr and Cs
(IOCP, 2024) Maachou, Aicha; Blizak, Salah; Nour El Hayet, Kamel; Moudira, Dalila; Rahala, Badis; Sarid, Ali; Mouheba, Yasmina; Kamariza, Soumia
This study investigates the in⿿uence of gamma radiation, emitted by a Cobalt-60 source, on the structural modi῿cations of a polysomatic ceramic of the Murataite type, intended for the containment of radioactive waste. The matrix is doped with Sr and Cs to simulate both radioactive alkaline and alkaline-earth isotopes. Samples are irradiated with a total dose of 105 Gy. After irradiation, the Archimedes density increases by 9.80% and 10.61% for undoped and Sr-doped ceramics, respectively. However, it decreases by 3.05% and 3.65% for Cs-doped ceramics and Sr-Cs co-doped ceramics, respectively. All measured values are below 4 g/cm3 . For all materials, the main XRD identi῿ed phase is 5M Murataite. After irradiation, this phase decreases signi῿cantly for both Cs and (Sr,Cs) doped materials, revealing that the particles movements under irradiation favours Cs and Sr-Cs hosting in the Zincohoegbomite secondary formed phase, which growth signi῿cantly after irradiation. The SEM observations reveal the crystalline grains morphological features, with few micrometers’ sizes. The ceramics’ Vickers microhardness is not a൵ected and ranges between 410 and 646 HV. In conclusion, both the reference material and Sr-Mur material composition are the optimum chemical composition and give the optimum murataites’ phase content after irradiation.
Magnetic properties of ultra-thin (Fe, Co) films coupled by Ir(001) spacers
(Elsevier, 2020) Kebaili, Aboubakr Seddik; Blizak, Salah; Bihlmayer, Gustav; Stefan, Blügel
We report on the magnetic properties of Fe1-xCox monolayers separated by Ir films ofvariable thickness, investigated using the full-potential linearized augmented plane-wave method based on the density functional theory. The interlayer exchange coupling can be used to mediate an exchange field between the layers, showing strong oscillations between antiferromagnetic and ferromagnetic coupling in terms of the Ir spacer thickness. For thin films (less than four Ir layers) a strong dependence on the chemical composition of the magnetic layers can be observed. We study also the magnetic anisotropy and the sensitivity of the in-plane exchange parameters of the magnetic layers to exchange coupling through the Ir spacer
Magnetic properties of ultra-thin (Fe, Co) films coupled by Ir(001) spacers
(Elsevier, 2020) Kebaili, Aboubakr Seddik; Blizak, Salah; Bihlmayer, Gustav; Blügel, Stefan
We report on the magnetic properties of Fe1-xCox monolayers separated by Ir films ofvariable thickness, investigated using the full-potential linearized augmented plane-wave method based on the density functional theory. The interlayer exchange coupling can be used to mediate an exchange field between the layers, showing strong oscillations between antiferromagnetic and ferromagnetic coupling in terms of the Ir spacer thickness. For thin films (less than four Ir layers) a strong dependence on the chemical composition of the magnetic layers can be observed. We study also the magnetic anisotropy and the sensitivity of the in-plane exchange parameters of the magnetic layers to exchange coupling through the Ir spacer
Modeling and Simulation of Magnons Scattering Across Shear Spins in Multilayered Ferromagnetic Slabs
(SPIN, 2021) Ferrah, Leila; Bourahla, Boualem; Blizak, Salah
In this work, we introduce a computer model and theoretical approach based on the matching technique to investigate the spin precession and the magnetic properties of an ordered magnetic interface joining two ferromagnetic multilayers of type AB, made of 10 spin slabs, obtained by alternative two spin layers A and B. We simulate, particularly, the coherent magnon transmission through spins' interface, in multilayered thin ̄lms, obtained by shearing a part of the ̄lm from the other at an angle of 30. The individual and total transmittance of bulk magnons of the thin ̄lm, scattering coherently at the shearing interface zone and the localized magnonic spin states, are calculated and analyzed. The transmission and re°ection spin modes are derived as elements of a Landauer–Büttiker type scattering matrix. The results highlight the localized spin states on the interface shear domain and their interactions with incident magnons. The evolutions of the magnonic spectra can be presented for arbitrary directions of the incident magnons on the boundary zone, for all accessible frequencies in the propagating bands as well as for the magnetic exchange coupling between each spin A(B) and its adjacent sites and their spin intensity. The results demonstrate the dependence of the magnonic spectra for the perfect multilayered ̄lms and at the inhomogeneous domain of the interface shear. The analysis of the spectra illustrates the °uctuations, related to Fano resonances, due to the coupling between travelling magnons and the localized modes in the shear interface domain. The calculated spectra could yield useful information concerning the magnetic parameters of such interface slabs in multilayered ̄lms.
Polycopié de cours : physique (niveau 1er année STH et ST)
(Université M'Hamed Bougara : Faculté des Hydrocarbures et de la Chimie, 2021) Blizak, Meriem Djanette; Blizak, Salah
Students’ perceptions regarding the abrupt transition to online learning during the COVID-19 Pandemic: Case of Faculty of Chemistry and Hydrocarbons at the University of Boumerdes—Algeria
(American Chemical Society, 2020) Blizak, Meriem Djanette; Blizak, Salah; Bouchenak, Ouahiba; Yahiaoui, Karima
In recent months, universities around the world have been forced to cancel courses and close their doors due to the growing coronavirus epidemic. Following the government’s precautions, Algerian students were bound to quarantine regulations for their safety. Thus, they unexpectedly switched to online learning instead of face-to-face learning. Our objective of this exploratory study is to investigate the perceptions of Algerian university students regarding the abrupt transition to online learning amid the COVID-19 pandemic. To achieve this goal, an online survey with closed and open-ended questions was conducted among 380 students from the faculty of chemistry and hydrocarbons (FCH) at the University of Boumerdes—Algeria. The results showed that students have a negative perception of online learning. They are reluctant about this new digital pedagogy and prefer the traditional way of teaching to online teaching during the coronavirus pandemic