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Artigos de revistas sobre o assunto "Alliages de Heusler – Propriétés électroniques"
Souici, Mounir, e Atika Roustila. "Rôle de l’hydrogène sur la microstructure et de la température sur les propriétés électroniques du nickel pur (Ni)". Journal of Renewable Energies 12, n.º 3 (26 de outubro de 2023). http://dx.doi.org/10.54966/jreen.v12i3.157.
Texto completo da fonteTeses / dissertações sobre o assunto "Alliages de Heusler – Propriétés électroniques"
Neggache, Amina. "Propriétés électroniques des alliages d'Heusler Co1.5Fe1.5Ge et Co2MnSi". Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0229/document.
Texto completo da fonteSpin transfer is one way of switching the magnetization of a layer in a magnetic tunnel junction. The current needed at this task depends on the materials and in the current context, consume less became an important issue. Materials with a high spin polarization and a low magnetic damping are one solution of this problem. They are called half metal ferromagnets. Because of the existence of a pseudo-gap in the minority spin channel at the Fermi energy, these compounds show a 100% spin polarization and an extremely low magnetic damping. In theory, some Heusler, such as Co1.5Fe1.5Ge and Co2MnSi, possess theses properties if they crystallize in the good crystallographic phase. In practice, there is strong indication of this behavior by mean of indirect techniques. However, no direct evidence of this pseudo-gap has been observed. It is in this context that this thesis is. After having determined growth conditions of Co1.5Fe1.5Ge, by mean of several techniques and especially by anomalous diffraction, we determined the complete chemical order which is the one we were looking for. Magnetic properties measurements show results in agreement with the theory. But the use of this compound in magnetic tunnel junctions shows low tunnel magnetoresistance. Spin resolved photoemission spectroscopy measurements explain very well these results. In the same spirit, we started to study Co2MnSi which seems more promising as this pseudo-gap and low magnetic damping have been observed
Palin, Victor. "Heusler compounds for spin-orbitronics : exploration of topological effects and magnetic anisotropy engineering". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0031.
Texto completo da fonteOver the last decades, the needs in storage capacity as shot up with computing development. The energy crisis that we are going through in the 21th century requires to develop new fundamental materials for data storage. It was with this purpose that physicist develop new ways to store information in order to reduce device’s scale, energy consumption and manufacturing cost while memories’ size and information’s speed has shot up. The research conducted in this thesis make use of two different ways to improve data storage:- The first one is by using emerging materials in science, called topological insulator, that host peculiar spin texture predicted to generate very high spin-to-charge interconversion. This non-trivial state of matter can be complex to stabilize and image. This is the goal of the first part of this thesis where topological insulators coming from the half-Heusler family are engineered by molecular beam epitaxy. Structural characterization are carried out by X-ray and electronic diffraction along with scanning tunneling microscopy and transmission electron microscopy that confirm an epitaxial growth in the desired structure predicted to host a non-trivial topology. Angle resolved photoemission spectroscopy is performed and reveals the presence of linear states around the Γ point of the Brillouin zone. Nonetheless, the complex Fermi surfaces imaged do not allow to draw clear conclusions on the non-trivial nature of both alloys. Transport measurements were performed to test the potential interconversion efficiency of our compounds and spin Seebeck experiments revealed a spin-to-charge conversion two to three times higher in our TIs compared to a Pt control sample.- The second way chosen to improve conventional magnetic memories is by playing with magnetic anisotropy. Here again, Heusler family offers a vast variety of compounds allowing to fulfill this goal. The Mn3Z family compounds has attracted a lot of attention owing to their tetragonalized unit cell that allows to stabilize perpendicular magnetic anisotropy (PMA) even in a thin film geometry. In this thesis, we investigate Mn(100-x)Ga(x) and Mn(100-x)Ge(x) alloys and manage to stabilize them in their D0(22) structure that offers PMA. A peculiar zoom is then done on Mn3Ge-based stacks composed of a second Heusler alloy with remarkable properties, the Co2MnZ’ family (Z' = Si, Ge). Co2MnZ’ compounds have a half-metallic behavior making them very suitable for spin transfer torque related applications due to their low magnetic damping and full spin polarization at the Fermi level. Here we develop Mn3Ge/Co2MnZ' heterostructures (bilayers and superlattices) and manage to grow both compounds in the desired structures. The overall system is perpendicularly magnetized (thanks to Mn3Ge), terminated with a half-metal magnet (thanks to Co2MnZ') and the thicknesses used for both layers allow to tune the magnetic properties and obtained 100% of remanence
Pradines, Barthélémy. "Structure électronique et propriétés magnétiques statiques et dynamiques d'alliages d'Heusler partiellement désordonnés et d'hétérostructures tout-Heusler". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30171/document.
Texto completo da fonteThe Heusler alloy family contains several compounds considered to be prime candidates to be integrated as magnetic electrode into high-?performance spintronic devices. Some of these alloys indeed exhibit high Curie temperatures, have been predicted theoretically to be half-?metallic, and display a low Gilbert damping parameter. Nevertheless, the experimental results are generally less convincing than those reported numerically. The first part of this thesis is devoted to the ab initio study of hypotheses that are usually used to explain the differences between experimental and theoretical results. Calculations, based on the density functional theory, are then used to understand the impact of structural defects (partial chemical disorders, tetragonal deformation, vacancies) on the static and dynamic electronic and magnetic properties of Co-?based bulk full-Heusler alloys (Co2MnSi, Co2MnSn, Co2MnAl et Co2FeAl). In the second part of this thesis we propose to study, with the same numerical tools, the physical characteristics of "all-Heusler" heterostructures promising for spintronics and rare in the literature. We have focused on the variations of electronic properties in the vicinity of the "half-metal/insulator" (Fe2TiSi/Co2MnSi, CoTiAs/Co2MnSi) or "half-metal/non-magnetic metal" (Fe2VAl/Co2MnSi, RhNiSi/Co2MnSi) interfaces composing the studied multilayers. The obtained results highlight the interest of these structures for spintronic devices such as spin valves or magnetic tunnel junctions
Abdallah, Iman. "Spin dynamics and structural modifications of Co2MnSi Heusler alloys by helium ions irradiation". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30079/document.
Texto completo da fonteSpintronic, which involve electron's in addition to its charge, has emerged from the discovery of Giant Magnetoresistance (GMR) by A. Fert and P. Grunberg in 1988, rewarded by a Nobel Prize in 2007. It has revolutionized the field of sensor devices. The basic mechanism of GMR and also of the Tunneling Magneto Resistance (TMR) relies on the spin polarization. Therefore there is today an intense research to find materials with both high spin polarization and low damping coefficient for the development of new generation of spintronic devices. In this field, one promising route concerns the Co2MnSi (CMS) Heusler alloy which is predicted to be half metals (i.e.100% spin polarization), with a weak Gilbert damping coefficient below 10-3, about one order of magnitude below the usual ferromagnetic material used in microelectronics. Its high Curie temperature up to 800° K also provides stability for devices working at room temperature. In this work, we study the correlations between the structural and magnetic properties of the Co2MnSi. To achieve our goal, we measure the evolution of the static and dynamic magnetic parameters of the Co2MnSi alloy in which atomic disorder is induced by He+ ion irradiation at 150 KeV. The samples are grown by magnetron sputtering on MgO substrates and then irradiated with light He+ ions. In order to correlate the structural and magnetic modifications of the alloy we combined several experimental techniques. CMS structure was investigated by X-ray diffraction and Transmission Electron Microscopy (TEM), in particular HAADF-STEM imaging mode. The evolution of the static and dynamic magnetic properties of the samples has been measured by means of Magneto Optic Kerr Effect (MOKE), Physical Properties Measurements System (PPMS) at the LPCNO laboratory in Toulouse and Ferromagnetic Resonance (FMR). The FMR set-up has been developed at the CEMES during this PhD. The main results of this work consists of correlation between the tetragonal deformations of the crystalline structure followed by the appearance of uniaxial anisotropy in the material upon irradiation. Furthermore, we demonstrate that the magnetic parameters of the B2 order are slightly affected by irradiation. But for the L21 phase, static and dynamic magnetic properties are drastically affected by irradiation, by the decrease in magnetization saturation, and exchange constant due to the Mn/Co disorder type and an increase of the cubic anisotropy and dynamic relaxation
Berger, Claire. "Propriétés électroniques des alliages quasicristallins AlMn". Grenoble 1, 1987. http://www.theses.fr/1987GRE10067.
Texto completo da fonteTuzcuoglu, Hanife. "Corrélation entre les propriétés structurales et magnétiques des couches minces et nanostructures de Co₂FeAl". Thesis, Paris 13, 2014. http://www.theses.fr/2014PA132035/document.
Texto completo da fonteACorrelation between structural and magnetic properties of Co₂FeAl thin films and nanostructures Co₂FeAl (CFA) is a very attractive Heusler alloy for spintronic applications. Their structural and magnetic properties depend strongly on the crystalline orientations and the interfaces quality. Therefore, the aim of this thesis is the study effects of the film thickness (dCFA), the substrate (MgO, Si and SrTiO₃(STO)) as well as the annealing temperature (Ta) on these properties. The structural analysis revealed a good epitaxial growth for films deposited on MgO and STO, in contrast to the Si substrate. The chemical order varies from the partially ordered B2 phase to the disordered A2 phase as dCFA or Ta decreases, regardless of the substrate. The ferromagnetic resonance (FMR) measurements show the superposition of a uniaxial and fourfold anisotropies for films grown on MgO and STO and only a weak uniaxial anisotropy for the samples grown on Si. The fourfold anisotropy is directly correlated to the crystal structure of the samples. The FMR and Brillouin light scattering measurements reveal the presence of a large negative perpendicular uniaxial anisotropy induced by CFA/MgO interface, which increases with 1/dCFA and with Ta. The relaxation mechanisms have carefully been studied and Gilbert damping coefficients of 0.0011 have been measured making CFA as a potential candidate for spin transfer torque-based devices. Finally, the study of submicron arrays of stripe obtained by patterning of the continuous CFA films reveals a spin waves quantization due to the finite stripes width
Mezhoudi, Amina. "Etude des propriétés électroniques et optiques d'alliages amorphes silicium azote préparés par pulvérisation réactive". Lyon 1, 1986. http://www.theses.fr/1986LYO19045.
Texto completo da fonteChaïb, Cheikh. "Contribution à l'étude des propriétés électroniques d'alliages métalliques liquides, métal noble-polyvalent, métal de transition-polyvalent". Metz, 1987. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1987/Chaib.Cheikh.SMZ8708.pdf.
Texto completo da fonteIn the present work we determine experimentally the electronic properties (resistivity and absolute thermoelectric power of metallic liquid alloys Cu-Pb and Mn-Sn. The theorical interpretation is in the frame work of Faber-Ziman theory. A new resistivity and TEP simultaneous measure cell has been elaborated. It is based on the fact that since the works of Roberts (1985), the tungsten can be taken as reference electrode for the TEP. Our attention has been fixed on the Cu-Pb system which presents a miscibility gap. Our aim was to determine if the presence of gap has an influence on electronic properties above the miscibility curve. We have studied the influence Bhatia-Thornton partials interference functions SNN and Snc which has been measured by neutron diffraction with the isotonic substitution method. The theoretical interpretation of the TEP of metallic ally can be realized according to the Faber-Ziman theory. The TEP is expressed as a function of energy dependent phase shifts. Anormal concentration dependence of the temperature coefficient of the resistivity and of the thermopower indicate some premonition of the phase separation. If we take into account the Bhatia-Thornton experimental interference functions, we improve considerably by resistivity calculation. Computation of TEP by using the energy dependence contribution the calculated TEP very new to the experimental one
Zaoui, Ali. "Etude des propriétés structurales, électroniques et optiques des semi-conducteurs de type AN B8-N et de leurs alliages". Metz, 1999. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1999/Zaoui.Ali.SMZ9943.pdf.
Texto completo da fonteOrtiz, Hernandez Guillermo. "Élaboration et étude des propriétés physiques de couches minces monocristallines d'alliage de Heusler à faible amortissement magnétique pour composants hyperfréquences". Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2045/.
Texto completo da fonteThis thesis fits in the framework of magnetic materials for microwave applications. The magnetic materials most commonly used in microwave devices are ferrites, especially garnets, which have a very low magnetic damping (about 0. 0001). The needs of miniaturization in current technologies bring some problems related to the integration of ferrites in microwave components. Theses materials, containing iron oxides, generally require very high deposition temperatures that may damage other parts within a same circuit. One solution lies in the use of ferromagnetic materials, which can be deposited at moderate temperatures. However, this type of material usually has high damping factors making them incompatible with the characteristics desired in microwave components. In this context, the Heusler alloys are particularly attractive. Indeed, the latter have high magnetizations and Curie temperatures, and ab initio calculations predict extremely low damping factors. The first step of this work was to develop a Ferromagnetic Resonance setup capable of studying materials in the microwave domain. This step was followed by the preparation of epitaxial thin film of Co2MnSi, by sputtering deposition, on MgO (001) and MgO/Cr (001) substrates. A thorough structural study (RHEED, X-ray diffraction, transmission electron microscopy) allowed verifying the high crystalline quality of samples. Their magnetic properties were studied by static and dynamic techniques in order to provide a complete characterization of their magnetic parameters as a function of thickness: saturation magnetization, exchange constant, damping factor, gyromagnetic ratio, anisotropy constants. The samples studied show low magnetic damping factors ranging between 0. 002 and 0. 007. The magnetic parameters (magnetocrystalline anisotropy, gyromagnetic factor) are strongly modified with the implementation of a Cr buffer layer. This suggests that the magnetic properties of Heusler alloys thin films are closely related to strains at interfaces. This work shows that Co2MnSi could constitute a building bloc for the realization of microwave components. The buffer layer engineering is set to be a key to making these alloys compatible with the needs of current technologies. This work should make possible the study of more complex systems such as magnonic crystals based on Heusler alloys
Livros sobre o assunto "Alliages de Heusler – Propriétés électroniques"
Illustrated Theatre Production Guide. Taylor & Francis Group, 2020.
Encontre o texto completo da fonteStribling, Zachary, e John Ramsey Holloway. Illustrated Theatre Production Guide. Taylor & Francis Group, 2020.
Encontre o texto completo da fonteStribling, Zachary, e John Ramsey Holloway. Illustrated Theatre Production Guide. Taylor & Francis Group, 2020.
Encontre o texto completo da fonteHolloway, John Ramsey. Illustrated Theatre Production Guide. Taylor & Francis Group, 2014.
Encontre o texto completo da fonteHolloway, John Ramsey. Illustrated Theatre Production Guide. Taylor & Francis Group, 2014.
Encontre o texto completo da fonteStribling, Zachary, e John Ramsey Holloway. Illustrated Theatre Production Guide. Taylor & Francis Group, 2020.
Encontre o texto completo da fonteStribling, Zachary, e John Ramsey Holloway. Illustrated Theatre Production Guide. Taylor & Francis Group, 2020.
Encontre o texto completo da fonteStribling, Zachary, e John Ramsey Holloway. Illustrated Theatre Production Guide. Taylor & Francis Group, 2020.
Encontre o texto completo da fonte