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5 results on '"Y. Dahmane"'

1. Magnetic and structural properties of electrodeposited CoPt and FePt nanowires in nanoporous alumina templates

Author

Y. Dahmane, L Cagnon, L. Ortega, J Voiron, N. Benbrahim, M. Bacia, Sébastien Pairis, A. Kadri, Laboratoire Louis Néel (LLN), and Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Acoustics and Ultrasonics, Annealing (metallurgy), Magnetism, Alloy, Nanowire, 02 engineering and technology, engineering.material, 01 natural sciences, Condensed Matter::Materials Science, Magnetization, Tetragonal crystal system, 0103 physical sciences, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Condensed matter physics, Nanoporous, Metallurgy, Coercivity, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], engineering, 0210 nano-technology
Abstract

CoPt and FePt nanowire arrays were successfully prepared by electrodeposition into nanochannels of porous alumina membranes. The as-deposited CoPt alloy has a face centred cubic structure and displays soft magnetic properties. Heat treatment at 700??C for different durations, under vacuum condition was carried out in order to obtain the ordered face centred tetragonal phase L10, exhibiting hard magnetic properties. After annealing, arrays of nanowires actually show hard magnetic properties with coercive fields up to 1.1?T at room temperature. Phase transformation, structural and magnetic properties were analysed and necessary conditions to obtain optimum magnetic properties are concluded.The first results obtained with FePt nanowires denote a more complicated system since the as-deposited material shows no magnetization. Magnetism appears only after annealing at 700??C minimum. Coercivity up to 1.1?T has been obtained at room temperature but with inhomogeneous phase composition.

Published
2006
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2. Heating asymmetry induced by tunneling current flow in magnetic tunnel junctions

Author

Clarisse Ducruet, R. C. Sousa, B. Dieny, C. Portemont, Y. Dahmane, Laurent Vila, K. Mackay, J.-P. Nozieres, Erwan Gapihan, Ioan Lucian Prejbeanu, J. Herault, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Service de Physique des Matériaux et Microstructures (SP2M - UMR 9002), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), CROCUS Technology, ANR-07-NANO-052-02 Project, and European Project: 246942,EC:FP7:ERC,ERC-2009-AdG,HYMAGINE(2010)

Subjects
010302 applied physics, [PHYS]Physics [physics], Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, Fermi level, 02 engineering and technology, Dissipation, 021001 nanoscience & nanotechnology, 01 natural sciences, symbols.namesake, Tunnel magnetoresistance, Exchange bias, Ballistic conduction, 0103 physical sciences, symbols, Current (fluid), 0210 nano-technology, Joule heating, Quantum tunnelling
Abstract

International audience; In this work, exchange bias was used as a probe to characterise the temperature profile induced by the inelastic relaxation of electrons tunnelling across a MgO barrier. Thermally assisted magnetic random access memory (TA-MRAM) cells comprising a magnetic tunnel junction (MTJ) with a reference pinned layer and a FeMn exchange biased storage layer were used. The pinning direction of the ferromagnetic storage layer is reversed when heated above the blocking temperature of the antiferromagnetic layer (FeMn). The power density required to reach this blocking temperature in the FeMn layer depends on the current polarity, indicating that the heat source term associated with the current flowing through the barrier depends itself on the current direction in contrast to simple Joule heating. This effect is due to the mechanism of energy dissipation in tunnelling. The tunnelling itself is ballistic i.e., without dissipation. However, after tunnelling, the hot electrons very quickly relax to the Fermi energy thereby loosing their excess energy in the receiving electrode. Therefore, the heat is essentially generated on one side of the barrier so that the whole profile of temperature throughout the pillar depends on the current direction. Full 3D thermal simulations also confirmed the temperature profile asymmetry. The proper choice of heating current direction (i.e., voltage polarity applied to the MTJ) can yield a reduction of about 10% in the heating power density required to enable writing in thermally assisted MRAM cells.

Published
2012
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3. Improved coherence of ultrafast spin-transfer-driven precessional switching with synthetic antiferromagnet perpendicular polarizer

Author

S. Auffret, Jean-Christophe Toussaint, Cristian Papusoi, Adrien Vaysset, S. Bandiera, Laurent Vila, M. Marins de Castro, Ursula Ebels, Liliana D. Buda-Prejbeanu, Y. Dahmane, B. Dieny, R. C. Sousa, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut National Polytechnique de Grenoble (INPG), Micro et NanoMagnétisme (NEEL - MNM), Institut Néel (NEEL), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS), Service de Physique des Matériaux et Microstructures (SP2M - UMR 9002), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), HYMAGINE (246942), European Project: 246942,EC:FP7:ERC,ERC-2009-AdG,HYMAGINE(2010), Micro et NanoMagnétisme (MNM), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)

Subjects
Physics, [PHYS]Physics [physics], Physics and Astronomy (miscellaneous), Condensed matter physics, business.industry, Demagnetizing field, 02 engineering and technology, Polarizer, 021001 nanoscience & nanotechnology, 01 natural sciences, Optical switch, law.invention, Optics, Planar, law, 0103 physical sciences, Physics::Space Physics, Perpendicular, 010306 general physics, 0210 nano-technology, business, Ultrashort pulse, Micromagnetics, Coherence (physics)
Abstract

International audience; The coherence of the precessional switching was compared in planar spin-valves comprising either an additional simple perpendicular polarizer or a synthetic antiferromagnet perpendicular polarizer. A significant improvement in the precession coherence was observed experimentally in the second type of samples. Micromagnetic simulations were performed to study the effect of the stray field from the perpendicular polarizer. They provide an explanation for the gradual loss of coherence of the precession in terms of vortex formation, which occurs much faster when a simple perpendicular polarizer is used.

Published
2011
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4. Comparison of Synthetic Antiferromagnets and Hard Ferromagnets as Reference Layer in Magnetic Tunnel Junctions With Perpendicular Magnetic Anisotropy

Author

B. Dieny, Vincent Baltz, C. Portemont, Stéphane Auffret, Sébastien Bandiera, Y. Dahmane, Ioan Lucian Prejbeanu, Clarisse Ducruet, R. C. Sousa, SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and CROCUS Technology

Subjects
010302 applied physics, Materials science, Condensed matter physics, Perpendicular magnetic anisotropy, Nanostructured materials, media_common.quotation_subject, Magnetic tunnelling, 02 engineering and technology, 021001 nanoscience & nanotechnology, Magnetic hysteresis, 01 natural sciences, Asymmetry, Electronic, Optical and Magnetic Materials, Dipole, Ferromagnetism, 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Layer (electronics), ComputingMilieux_MISCELLANEOUS, media_common
Abstract

In magnetic tunnel junctions (MTJ), synthetic antiferromagnets (SAF) are usually used as reference layer to minimize dipolar interactions induced between this layer and the free layer (FL). We show here that the use of SAF allows us to reduce the asymmetry of the FL reversal due to stray fields in nanosized MTJs with perpendicular magnetic anisotropy.

Published
2010
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5. Electrodeposited CoPt and FePt alloys nanowires

Author

N. Benbrahim, A. Kadri, M. Bacia, Laurent Cagnon, J. Voiron, Y. Dahmane, Sébastien Pairis, L. Ortega, Micro et NanoMagnétisme (MNM), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Optique et microscopies (POM), X'Press (X'Press), Laboratoire de physique et de chimie des matériaux [Tizi-Ouzou] (LPCM), Université Mouloud Mammeri [Tizi Ouzou] (UMMTO), Laboratoire d'Etude des Matériaux Optoélectronique & Polymères, University of Oran, Micro et NanoMagnétisme (NEEL - MNM), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS), Croissance Cristalline et MicroAnalyse (NEEL - C2MA), and X'Press : diffraction et hautes pressions (NEEL - X'Press)

Subjects
Materials science, Condensed matter physics, Annealing (metallurgy), Magnetism, Nanowire, 02 engineering and technology, Coercivity, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Magnetocrystalline anisotropy, Microstructure, 01 natural sciences, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Magnetization, Magnetic anisotropy, Nuclear magnetic resonance, High coercivity materials, Magnetic recording materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; We have investigated CoPt and FePt alloys with the face centered tetragonal phase L10, which present very large magnetocrystalline anisotropy. Equiatomic CoPt nanowires exhibiting large coercive fields up to 1.1 T have been successfully prepared by electrodeposition into nanopores of commercial and home-made alumina membranes from a very simple electrolyte. The as-deposited material has the FCC structure with soft magnetic properties. An annealing treatment at 700 °C is crucial to transform this phase into the L1 0 phase, which presents hard magnetic properties. Nanowires of annealed samples consist of small grains around 20 nm, with their c axes randomly distributed. The coercivity does not depend on the morphology and porosity of the two types of membranes but only on the deposited material elaborated with the appropriate thermal annealing process. Our preliminary results with FePt alloy indicate a more complicated system since the as-deposited material shows no magnetization. Magnetism appears only after annealing at 700-750 °C. Coercivity up to 0.85 T has been obtained at room temperature but with inhomogeneous phase composition. To achieve a single hard phase L1 0, it is essential to get for the as-deposited sample the equiatomic composition and then to employ the suitable annealing parameters (temperature and time) to change the whole FCC phase into the FCT ordered L1 0 phase.

Published
2007
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