Publications Internationales

Permanent URI for this collectionhttps://dspace.univ-boumerdes.dz/handle/123456789/13

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Author: search.filters.author.Guittoum, A.Subject: search.filters.subject.Magnetic properties

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    Hydrothermal synthesis of co nanoparticles : structure, morphology and magnetic properties
    (World Scientific, 2021) Bouelkreb, I.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Blanco, J. A.; Boukherroub, N.
    We have investigated the crystal structure, the microstructural and morphological characteristics, as well as the magnetic properties of Co nanoparticles (NPs) synthesized by a hydrothermal method. A series of samples has been elaborated for different concentrations of sodium hydroxide. The analysis of X-ray diffraction patterns, using two different wavelengths, has evidenced the coexistence of both α-Co and β-Co phases in the samples. The lattice parameter for both phases is in good agreement with those values expected for their bulk Co counterparts; the grain sizes of NPs were found to be dependent on the NaOH concentration. The scanning electron microscope micrographs show that Co NPs are agglomerated forming micrometer-sized entities whose shape evolves, indicating that the synthesis process affects the morphology of the powdered samples. Magnetic measurements indicate that the coercivity is slightly larger, HC>200 Oe, for Co NPs with dendritic-like shape, probably due to an increase in the magnetocrystalline anisotropy
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    The role of silicon on the microstructure and magnetic behaviour of nanostructured (Fe0.7Co0.3)100_xSix powders
    (Elsevier, 2017) Hocine, M.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Rahal, B.; Blanco, J.A.; Sunol, J.J.; Laggoun, A.
    Single-phase(Fe0.7Co0.3)100 xSix nanostructured powders(x¼0,5, 10,15and20)havebeenelaboratedby mechanical alloyinginordertoinvestigatetheeffectofsilicononthemicrostructureandmagnetic properties ofthesealloys.AdisorderedFe(Co,Si)solidsolutionwithbodycentredcubic(bcc)crystal structure isformedafter72hofmillingforallthecompositions.TheadditionofSigivesrisetoapro- gressivedecreaseofthelatticeparameter,fromabout2.865ÅforthebinaryFe70Co30 compound downto 2.841Åforthepowderwith x¼20. ThesamplewiththeuppermostSicontentexhibitsthelowestvalue for themeangrainsize(E10nm)aswellasthelargestmicrostrain(above1.1%).Allthesamplesare ferromagnetic atroomtemperature,althoughthesaturationmagnetizationvaluereducesalmostlinearly by addingSitothecomposition.Asimilartrendisobservedforthehyperfine magnetic field obtained from theanalysisoftheroomtemperatureMössbauerspectra.Thehyperfine field distributionsshowa broad double-peakshapefor x40, whichcanbeascribedtomultiplelocalenvironmentsfortheFe atoms insideadisorderedsolidsolution
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    Microstructure and magnetic properties of nanostructured (Fe0.8Al0.2)100-xSix alloy produced by mechanical alloying
    (Elsevier, 2015) Boukherroub, Nadia; Guittoum, A.; Laggoun, A.; Hemmous, M.; Martínez-Blanco, D.; Blanco, J.A.; Souami, N.; Gorria, P.; Bourzami, A.; Lenoble, O.
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    A comparative structural and magnetic study of Fe100-xPdx(x=15, 20 and 36) thin films deposited on Si (100) and glass substrates
    (Elsevier, 2015) Bahamida, Saida; Fnidiki, A.; Laggoun, A.; Guittoum, A.
    Various structural and magnetic characterization techniques have been used to investigate Fe100-xPdx (x=15, 20 and 36) thin films deposited onto silicon and glass substrates, by thermal evaporation technique. X-ray diffraction analysis shows the presence of supersaturated solid solution with bcc structure for Pd concentrations of 15% and 20%. However, for 36% of Pd, in addition to the supersaturated α-FePd (bcc) phase, another disordered FePd3 phase with fcc structure is present. At 20 at% Pd, the magnetic characterization shows a saturation of the bcc (α-FePd) phase and the appearance of the fcc phase. The correlation between the structure and magnetic properties allows us to compare the two substrates effects on deposited thin films. As results, the measurements indicate that the grain size D, the thin film thickness and the d(110) spacing significantly affect the magnetic coercivity HC. The Fe-Pd alloys deposited on a monocrystalline Si (100) and glass substrate show that the coercivity HC is given by the random anisotropy model. & 2015