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1. Exchange stiffness in ultrathin perpendicularly magnetized CoFeB layers determined using the spectroscopy of electrically excited spin waves

Author

Ricardo Sousa, Bernard Dieny, Thibaut Devolder, Bernard Rodmacq, Joo-Von Kim, L. E. Nistor, Institut d'électronique fondamentale (IEF), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), 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), ANR-11-BS10-0003,NanoSWITI,Nanoscale manipulation of spin waves in itinerant ferromagnets: technologies and fundamentals(2011), and ANR-14-CE26-0012,ULTRASKY,Skyrmions dans les couches magnétiques ultraminces en vue d'une spintronique basse consommation(2014)

Subjects
Materials science, Condensed matter physics, General Physics and Astronomy, Stiffness, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Magnetization, Spin wave, Excited state, 0103 physical sciences, medicine, Perpendicular, medicine.symptom, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Spectroscopy, Micromagnetics, ComputingMilieux_MISCELLANEOUS, Nanopillar
Abstract

We measure the frequencies of spin waves in nm-thick perpendicularly magnetized FeCoB systems, and model the frequencies to deduce the exchange stiffness of this material in the ultrathin limit. For this, we embody the layers in magnetic tunnel junctions patterned into circular nanopillars of diameters ranging from 100 to 300 nm, and we use magneto-resistance to determine which rf-current frequencies are efficient in populating the spin wave modes. Micromagnetic calculations indicate that the ultrathin nature of the layer and the large wave vectors used ensure that the spin wave frequencies are predominantly determined by the exchange stiffness, such that the number of modes in a given frequency window can be used to estimate the exchange stiffness. For 1 nm layers, the experimental data are consistent with an exchange stiffness A=20±2 pJ/m, which is slightly lower than its bulk counterpart. The thickness dependence of the exchange stiffness has strong implications for the numerous situations that involve...

Published
2016
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2. Perpendicular magnetic tunnel junctions with double barrier and single or synthetic antiferromagnetic storage layer

Author

Stéphane Auffret, Bernard Rodmacq, Bernard Dieny, Ricardo C. Sousa, Léa Cuchet, I. L. Prejbeanu, 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), ANR-13-NANO-0010,EXCALYB,Cellules MRAM sub-20nm et intégration CMOS de circuits hybrides(2013), and European Project: 246942,EC:FP7:ERC,ERC-2009-AdG,HYMAGINE(2010)

Subjects
[PHYS]Physics [physics], Materials science, Condensed matter physics, Spin-transfer torque, General Physics and Astronomy, Tunnel effect, Ferromagnetism, Random-Access Memory, Perpendicular, Antiferromagnetism, Anisotropy, Thermal stability, Condensed Matter::Strongly Correlated Electrons, Antiparallel (electronics)
Abstract

International audience; The magnetic properties of double tunnel junctions with perpendicular anisotropy were investigated. Two synthetic antiferromagnetic references are used, while the middle storage magnetic layer can be either a single ferromagnetic or a synthetic antiferromagnetic FeCoB-based layer, with a critical thickness as large as 3.0 nm. Among the different achievable magnetic configurations in zero field, those with either antiparallel references, and single ferromagnetic storage layer, or parallel references, and synthetic antiferromagnetic storage layer, are of particular interest since they allow increasing the efficiency of spin transfer torque writing and the thermal stability of the stored information as compared to single tunnel junctions. The latter configuration can be preferred when stray fields would favour a parallel orientation of the reference layers. In this case, the synthetic antiferromagnetic storage layer is also less sensitive to residual stray fields. (C) 2015 AIP Publishing LLC.

Published
2015
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3. Field Dependence of Spin-Transfer Torque Switching Current in Perpendicular Magnetic Tunnel Junctions

Author

Ricardo Sousa, Bernard Rodmacq, Bernard Dieny, Léa Cuchet, Laurent Vila, Stéphane Auffret, 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)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Materials science, Condensed matter physics, Spin-transfer torque, Field dependence, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, 0103 physical sciences, Perpendicular, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Torque, Critical current, Electrical and Electronic Engineering, Current (fluid), 010306 general physics, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS, Nanopillar
Abstract

Spin-transfer torque switching has been studied on (Co/Pt)/Ta/CoFeB/MgO/FeCoB/Ta patterned perpendicular magnetic tunnel junctions with nanopillar diameters ranging between 100 and 300 nm. Plotting current-field state diagrams, the critical current density for writing was found to be around 3 MA· cm -2 . The field-current dependence of the state transition boundary is linear, with the slope depending on material parameters. Using different thicknesses of top FeCoB free layers, we were able to estimate the Gilbert damping parameter α .

Published
2014
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4. Size dependence of magnetic switching in perpendicularly magnetized MgO/Co/Pt pillars close to the spin reorientation transition

Author

Wolfgang Kuch, Bernard Rodmacq, W. Stefanowicz, Gilles Gaudin, Jan Vogel, Liliana D. Buda-Prejbeanu, Stefania Pizzini, Stéphane Auffret, Lavinia Elena Nistor, 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), Institut für Experimentalphysik (FU BERLIN), Freie Universität Berlin, 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), 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
010302 applied physics, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, chemistry.chemical_element, 02 engineering and technology, Coercivity, 021001 nanoscience & nanotechnology, 01 natural sciences, Magnetization, chemistry, Remanence, 0103 physical sciences, Perpendicular, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Single domain, 0210 nano-technology, Micromagnetics, Cobalt, Spin-½
Abstract

International audience; We investigated the magnetic switching of MgO/Co/Pt pillars with perpendicular magnetic anisotropy, for lateral pillar sizes from 30 nm to 2 lm and for Co layer thicknesses between 1.8 and 2.6 nm. For large pillars, both the coercivity and the remanent magnetization decrease for increasing Co thickness. For all Co thicknesses, the coercivity strongly increases upon decreasing the pillar size. A comparison with micromagnetic simulations shows that the change in coercivity is determined by size-dependent demagnetizing effects. Our results show that small pillars with perpendicular magnetization and a tunable coercivity can be fabricated from continuous layers with in-plane magnetization.

Published
2014
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5. Influence of a Ta spacer on the magnetic and transport properties of perpendicular magnetic tunnel junctions

Author

Bernard Dieny, Clarisse Ducruet, Léa Cuchet, Bernard Rodmacq, Stéphane Auffret, Ricardo C. Sousa, SPINtronique et TEchnologie des Composants (SPINTEC), 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)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), ANR-10-NANO-0013,PATHOS,Matériaux à Anisotropie Perpendiculaire pour cellules Mémoire Magnétiques Non-volatiles Haute-densité(2010), European Project: 246942,EC:FP7:ERC,ERC-2009-AdG,HYMAGINE(2010), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
010302 applied physics, [PHYS]Physics [physics], Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, Tantalum, chemistry.chemical_element, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Magnetization, Magnetic anisotropy, Tunnel magnetoresistance, Condensed Matter::Materials Science, Nuclear magnetic resonance, chemistry, Condensed Matter::Superconductivity, 0103 physical sciences, Electrode, Perpendicular, Coupling (piping), 0210 nano-technology, Layer (electronics)
Abstract

International audience; Ultrathin Ta layers were inserted in the bottom hard (Co/Pt)/Ta/CoFeB/MgO magnetic electrode of perpendicular magnetic tunnel junctions. The magnetization of the top part of this electrode abruptly falls in-plane when the Ta thickness exceeds 0.45 nm. This results from the balance between the various energy terms acting on this layer (exchange-like coupling through Ta, demagnetizing energy, and perpendicular anisotropy at the CoFeB/MgO interface). For small Ta thicknesses, this insertion leads to a strong improvement of the tunnel magnetoresistance, as long as the magnetization of all layers remains perpendicular-to-plane.

Published
2013
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6. Direct Observation of Massless Domain Wall Dynamics in Nanostripes with Perpendicular Magnetic Anisotropy

Author

Stéphane Auffret, Jan Vogel, Olivier Boulle, Ioan Mihai Miron, Bernard Rodmacq, Fausto Sirotti, Julio C. Cezar, Gilles Gaudin, Nicolas Rougemaille, Stefania Pizzini, Marlio Bonfim, Micro et NanoMagnétisme (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), 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), European Synchrotron Radiation Facility (ESRF), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), and Micro et NanoMagnétisme (NEEL - MNM)

Subjects
media_common.quotation_subject, General Physics and Astronomy, FOS: Physical sciences, 02 engineering and technology, Inertia, 01 natural sciences, spin torque, 0103 physical sciences, 010306 general physics, media_common, Physics, Condensed Matter - Materials Science, Condensed matter physics, domain walls, Materials Science (cond-mat.mtrl-sci), Nanosecond, inertia, 021001 nanoscience & nanotechnology, Pulse (physics), 75.70.Ak, 75.60.Jk, 07.85.Qe, 75.50.Bb, Massless particle, Domain wall (magnetism), Amplitude, magnetic nanostripes, Domain (ring theory), [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Constant (mathematics)
Abstract

Domain wall motion induced by nanosecond current pulses in nanostripes with perpendicular magnetic anisotropy ($\mathrm{Pt}/\mathrm{Co}/{\mathrm{AlO}}_{x}$) is shown to exhibit negligible inertia. Time-resolved magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low ``mass'' of these domain walls is attributed to the combination of their narrow width and high damping parameter $\ensuremath{\alpha}$. Such a small inertia should allow accurate control of domain wall motion by tuning the duration and amplitude of the current pulses.

Published
2012
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7. Expansion and relaxation of magnetic mirror domains in a Pt/Co/Pt/Co/Pt multilayer with antiferromagnetic interlayer coupling

Author

Peter J. Metaxas, J.P. Jamet, Robert Stamps, Vincent Baltz, Jacques Ferré, Bernard Rodmacq, The University of Western Australia (UWA), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), SUPA School of Physics and Astronomy [Glasgow], University of Glasgow, 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)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
010302 applied physics, Physics, Condensed matter physics, Field (physics), Magnetism, Relaxation (NMR), Condensed Matter Physics, 01 natural sciences, Magnetic mirror, Dipole, 0103 physical sciences, Domain (ring theory), Perpendicular, Antiferromagnetism, General Materials Science, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, ComputingMilieux_MISCELLANEOUS
Abstract

We detail measurements of field-driven expansion and zero-field relaxation of magnetic mirror domains in antiferromagnetically coupled perpendicularly magnetized ultrathin Co layers. The zero-field stability of aligned ('mirror') domains in such systems results from non-homogeneous dipolar stray fields which exist in the vicinity of the domain walls. During field-driven domain expansion, we evidence a separation of the domain walls which form the mirror domain boundary. However, the walls realign, thereby reforming a mirror domain, if their final separation is below a critical distance at the end of the field pulse. This critical distance marks the point at which the effective net interaction between the walls changes from attractive to repulsive.

Published
2012
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8. Dynamic Binding of Driven Interfaces in Coupled Ultrathin Ferromagnetic Layers

Author

Robert Stamps, Peter J. Metaxas, Jacques Ferré, J.P. Jamet, Vincent Baltz, Paolo Politi, Bernard Rodmacq, The University of Western Australia (UWA), Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), 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), Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, and Consiglio Nazionale delle Ricerche

Subjects
Condensed Matter - Materials Science, Materials science, Field (physics), Condensed matter physics, Dynamic interface, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, General Physics and Astronomy, Disordered Systems and Neural Networks (cond-mat.dis-nn), 02 engineering and technology, Condensed Matter - Disordered Systems and Neural Networks, 021001 nanoscience & nanotechnology, 16. Peace & justice, 01 natural sciences, Domain (mathematical analysis), PACS numbers: 75.60.Ch, 75.78.Fg, 75.70.Cn, Ferromagnetism, 0103 physical sciences, Bound state, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Layer (electronics)
Abstract

We demonstrate experimentally dynamic interface binding in a system consisting of two coupled ferromagnetic layers. While domain walls in each layer have different velocity-field responses, for two broad ranges of the driving field, H, walls in the two layers are bound and move at a common velocity. The bound states have their own velocity-field response and arise when the isolated wall velocities in each layer are close, a condition which always occurs as H->0. Several features of the bound states are reproduced using a one dimensional model, illustrating their general nature., 5 pages, 4 figures, to be published in Physical Review Letters

Published
2010
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9. Bimodal distribution of blocking temperature in exchange-biased ferromagnetic/antiferromagnetic bilayers

Author

A. Zarefy, Bernard Rodmacq, Vincent Baltz, L. Lechevallier, Bernard Dieny, 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), Groupe de physique des matériaux (GPM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU), Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010302 applied physics, Blocking (linguistics), Materials science, Condensed matter physics, Spins, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Electronic, Optical and Magnetic Materials, Geomagnetic reversal, Distribution (mathematics), Exchange bias, Ferromagnetism, 0103 physical sciences, Antiferromagnetism, Condensed Matter::Strongly Correlated Electrons, Crystallite, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Computer Science::Operating Systems
Abstract

The blocking temperature $({T}_{\text{B}})$ distribution of various polycrystalline ferromagnetic (F)/antiferromagnetic (AF) bilayers exhibits two distinct peaks. This is ascribed to the existence of two families of magnetic entities determining the temperature dependence of exchange bias. One is formed by the AF grains which undergo thermally activated magnetic reversal. The other is formed by F/AF disordered interfacial spins which exhibit spin-glass-like behavior. The bulk versus interfacial nature of these two families is indicated by the dependence of the ${T}_{\text{B}}$ distribution on the AF thickness.

Published
2010
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10. Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer

Author

Stéphane Auffret, Ioan Mihai Miron, Bernard Rodmacq, Alain Schuhl, Jan Vogel, Gilles Gaudin, Pietro Gambardella, Stefania Pizzini, 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), Centre d'Investigació en Nanociència i Nanotecnologia, ICN-CSIC, Micro et NanoMagnétisme (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), Micro et NanoMagnétisme (NEEL - MNM), and European Research Council

Subjects
perpendicular magnetic anisotropy, 02 engineering and technology, 01 natural sciences, 7. Clean energy, Magnetization, Condensed Matter::Materials Science, Electric field, 0103 physical sciences, General Materials Science, 010306 general physics, ComputingMilieux_MISCELLANEOUS, Physics, spin-orbit torque, Condensed matter physics, Spin polarization, Spintronics, Mechanical Engineering, Spin-transfer torque, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Ferromagnetic resonance, Magnetic field, Mechanics of Materials, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, magnetization reversal, Rashba, Rashba effect
Abstract

5 páginas, 4 figuras.-- et al., Methods to manipulate the magnetization of ferromagnets by means of local electric fields or current-induced spin transfer torque allow the design of integrated spintronic devices with reduced dimensions and energy consumption compared with conventional magnetic field actuation. An alternative way to induce a spin torque using an electric current has been proposed based on intrinsic spin–orbit magnetic fields and recently realized in a strained low-temperature ferromagnetic semiconductor. Here we demonstrate that strong magnetic fields can be induced in ferromagnetic metal films lacking structure inversion symmetry through the Rashba effect. Owing to the combination of spin–orbit and exchange interactions, we show that an electric current flowing in the plane of a Co layer with asymmetric Pt and AlOx interfaces produces an effective transverse magnetic field of 1 T per 108 A cm−2. Besides its fundamental significance, the high efficiency of this process makes it a realistic candidate for room-temperature spintronic applications., This work was supported by the European Research Council (Starting Grant 203239).

Published
2010
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11. Effect of electrical current pulses on domain walls in Pt/Co/Pt nanotracks with out-of-plane anisotropy: Spin transfer torque versus Joule heating

Author

Vincent Baltz, André Thiaville, N. Charpentier, Alexandra Mougin, Bernard Rodmacq, Raphaël Weil, F. Piéchon, M. Cormier, Jacques Ferré, Laboratoire de Physique des Solides (LPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), 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)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Materials science, Condensed matter physics, Magnetic domain, Demagnetizing field, Spin-transfer torque, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Electronic, Optical and Magnetic Materials, Nuclear magnetic resonance, 0103 physical sciences, Current (fluid), [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Anisotropy, Joule heating, Current density, Spin-½
Abstract

International audience; The effect of electrical current pulses on magnetic domain walls is studied in a nanometer-scale magnetic track defined in a He +-irradiated Pt/Co0.5 nm/Pt film with out-of-plane anisotropy. Current pulses in a wide range of intensities and durations are shown to result either in track demagnetization, or in polarity-independent domain-wall propagation, due to Joule heating during the current pulse. None of the expected spin transfer effects is shown to occur. To explain this, the spin-dependent current-density distribution in the stack is evaluated, in the frame of an adapted Fuchs-Sondheimer model. The spin-polarized current density in the cobalt layer is shown to be unexpectedly low as compared to the charge current in the whole stack, which causes Joule heating. This is explained by a low electron transmission at Co/Pt interfaces, as is deduced from resistance measurements on a series of samples with different cobalt thicknesses. This leads us to emphasize that the balance between spin and total charge current densities should be carefully considered when addressing spin transfer torque effects.

Published
2010
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12. Investigation of metallic/oxide interfaces in Pt/Co/AlOx trilayers by hard x-ray reflectivity

Author

P. Plaindoux, H. Garad, B. Zawilski, Bernard Dieny, F. Fettar, Stéphane Auffret, Bernard Rodmacq, Luc Ortega, A.Y. Ramos, Surfaces, Interfaces et Nanostructures (SIN), 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), X'Press (X'Press), Matériaux, Rayonnements, Structure (MRS), Automatisation et Caractérisation (AUTOCARAC), 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), Surfaces, Interfaces et Nanostructures (NEEL - SIN), 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), X'Press : diffraction et hautes pressions (NEEL - X'Press), Matériaux, Rayonnements, Structure (NEEL - MRS), and Automatisation & caractérisation (NEEL - AUTOCARAC)

Subjects
Materials science, oxidation, perpendicular magnetic anisotropy, Analytical chemistry, Oxide, chemistry.chemical_element, 02 engineering and technology, 01 natural sciences, Metal, chemistry.chemical_compound, reflectometry X-ray chemical analysis, Hall effect, 0103 physical sciences, Magnetic layered films, Electrical and Electronic Engineering, 010306 general physics, Magnetic structure, Condensed matter physics, 021001 nanoscience & nanotechnology, Electronic, Optical and Magnetic Materials, X-ray reflectivity, Magnetic anisotropy, chemistry, metal-insulator structures, visual_art, visual_art.visual_art_medium, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], X-ray measurements, 0210 nano-technology, Platinum, Cobalt
Abstract

International audience; X-ray reflectivity (XRR) is used to determine the oxidation front at the nanometer scale in sputtered perpendicular semi tunnel junctions, as the form Pt/Co/AlOx, by varying the oxidation time tOx of the capping layer. From XRR simulations, we show that the nature of the stack is gradually defined according to the value of tOx. For low tOx values (

Published
2009
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13. High domain wall velocities induced by current in ultrathin Pt/Co/AlOx wires with perpendicular magnetic anisotropy

Author

Gilles Gaudin, T. A. Moore, Stefania Pizzini, G. Serret, Stéphane Auffret, Alain Schuhl, Bernard Rodmacq, Marlio Bonfim, Ioan Mihai Miron, Jan Vogel, 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), 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), Departamento de Engenharia Elétrica, Universidade Federal do Paraná (UFPR), ANR-07-NANO-0034,DYNAWALL,Magnetic domain wall dynamics induced by spin polarised current(2007), Micro et NanoMagnétisme (NEEL - MNM), and 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)

Subjects
Materials science, Physics and Astronomy (miscellaneous), Kerr microscopy, Perpendicular magnetic anisotropy, FOS: Physical sciences, 02 engineering and technology, domain wall, 01 natural sciences, spin torque, Current pulse, perpendicular anisotropy, 0103 physical sciences, ComputingMilieux_MISCELLANEOUS, 010302 applied physics, Condensed matter physics, 021001 nanoscience & nanotechnology, Condensed Matter - Other Condensed Matter, Domain wall (magnetism), Amplitude, Creep, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], PACS : 75.70.Kw, 75.60.Ch, 75.30.Gw, 78.20.Ls, Current (fluid), 0210 nano-technology, Displacement (fluid), Current density, Other Condensed Matter (cond-mat.other)
Abstract

Current-induced domain wall (DW) displacements in an array of ultrathin Pt/Co/AlOx wires with perpendicular magnetic anisotropy have been directly observed by wide field Kerr microscopy. DWs in all wires in the array were driven simultaneously and their displacement on the micrometer-scale was controlled by the current pulse amplitude and duration. At the lower current densities where DW displacements were observed (j less than or equal to 1.5 x 10^12 A/m^2), the DW motion obeys a creep law. At higher current density (j = 1.8 x 10^12 A/m^2), zero-field average DW velocities up to 130 +/- 10 m/s were recorded., Comment: Minor changes to Fig. 1(b) and text, correcting for the fact that domain walls were subsequently found to move counter to the electron flow. References updated

Published
2008
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14. Multilevel magnetic nanodot arrays with out of plane anisotropy: the role of intra-dot magnetostatic coupling

Author

Vincent Baltz, J.P. Jamet, Jacques Ferré, Alberto Bollero, Bernard Rodmacq, Bernard Dieny, 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), Laboratoire de Physique des Solides (LPS), and Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Coupling, Materials science, Nanostructure, Condensed matter physics, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 01 natural sciences, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Amplitude, Transition metal, 0103 physical sciences, Nanodot, Single domain, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Anisotropy, Instrumentation, Layer (electronics)
Abstract

International audience; Intra-dot inter-layer magnetostatic coupling have been investigated in trilayers which consist of two [Co/Pt] multilayers with out-of-plane anisotropy and different coercivities separated by a thick Pt layer. For single domain nanodots, the strong intra-dot inter-layer magnetostatic interactions manifest as a shift of the soft layer hysteresis loop. The amplitude of this shift decreases when the size of the dots is increased and/or when the temperature is increased. Satisfactory agreement is found between calculations and experimental results. PACS. 75 Magnetic properties and materials-75.70.-i Magnetic properties of thin films, surfaces, and interfaces-75.60.-d Domain effects, magnetization curves, and hysteresis-75.60.Ch Domain walls and domain structure-75.75.+a Magnetic properties of nanostructures

Published
2007
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15. Magnetic behavior of systems composed of coupled ferromagnetic bilayers with distinct anisotropy directions

Author

Bernard Dieny, Liliana D. Buda-Prejbeanu, Vincent Baltz, Jordi Sort, Bernard Rodmacq, Alberto Bollero, 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 Universitat Autònoma de Barcelona (UAB)

Subjects
010302 applied physics, Materials science, Condensed matter physics, Magnetic domain, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Magnetic hysteresis, 01 natural sciences, Magnetic susceptibility, Electronic, Optical and Magnetic Materials, Magnetic anisotropy, Magnetization, Condensed Matter::Materials Science, Exchange bias, 0103 physical sciences, Single domain, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Saturation (magnetic)
Abstract

A shift in the hysteresis loop of a $\mathrm{NiFe}$ thin film (with in-plane anisotropy) exchange coupled to a $[\mathrm{Pt}∕\mathrm{Co}]$ multilayer (with out-of-plane anisotropy) is observed after in-plane saturation of the system. The origin of this effect and the related magnetic properties are investigated by means of in-plane and out-of-plane magnetometry techniques, magnetic force microscopy imaging, and micromagnetic simulations. Both the number of $\mathrm{Pt}∕\mathrm{Co}$ repetitions in the multilayer and the $\mathrm{NiFe}$ thickness are found to have an influence on the magnitude of the loop shift and the in-plane and out-of-plane coercivity values of the system. This is correlated with variations in the number and average size of the magnetic domains formed in the $[\mathrm{Pt}∕\mathrm{Co}]$ multilayer which, as revealed by micromagnetic simulations, pin the $\mathrm{NiFe}$ magnetization via formation of closure domains with a preferential orientation at the interface between the $[\mathrm{Pt}∕\mathrm{Co}]$ multilayer and the $\mathrm{NiFe}$.

Published
2006
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16. Multilevel magnetic media in continuous and patterned films with out-of-plane magnetization

Author

Bernard Dieny, Bernard Rodmacq, S. Landis, Vincent Baltz, 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), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), and Direction de Recherche Technologique (CEA) (DRT (CEA))

Subjects
010302 applied physics, Materials science, Magnetic domain, Condensed matter physics, 02 engineering and technology, Coercivity, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Electronic, Optical and Magnetic Materials, Condensed Matter::Materials Science, Magnetization, Magnetic anisotropy, Ferromagnetism, 0103 physical sciences, Patterned media, Nanodot, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Anisotropy, ComputingMilieux_MISCELLANEOUS
Abstract

In conventional high-density magnetic media, information is stored in the form of magnetic domains oriented in two possible remanent states along an easy axis of anisotropy. In order to further increase the areal density keeping the same bit size, multilevel magnetic media consisting of N decoupled ferromagnetic storage layers ( N ⩾2) with different coercivities can be used. In such a case, the recording media exhibit up to 2 N stable remanent states. In this study, decoupled (Co/Pt) multilayers systems with perpendicular anisotropy have been sputtered on continuous silicon substrates and arrays of pre-patterned silicon nanodots in order to achieve magnetic continuous and patterned multilevel media. These media were characterized from a magnetic point of view.

Published
2005
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17. Magnetic relaxation of exchange biased (Pt/Co) multilayers studied by time-resolved Kerr microscopy

Author

Marlio Bonfim, Fabien Romanens, Julio Camarero, Bernard Dieny, Stefania Pizzini, Flávio Garcia, Jan Vogel, Yan Pennec, Bernard Rodmacq, Fabiano Yokaichiya, Jordi Sort, Laboratoire Louis Néel (LLN), Centre National de la Recherche Scientifique (CNRS), Departamento de Engenharia Elétrica, Universidade Federal do Paraná (UFPR), Departamento de Fisica de la Materia Condensada [Madrid] (FMC), Facultad de Ciencas [Madrid], Universidad Autonoma de Madrid (UAM)-Universidad Autonoma de Madrid (UAM), 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 Universidad Autónoma de Madrid (UAM)-Universidad Autónoma de Madrid (UAM)

Subjects
Kerr effect, Materials science, Magnetic domain, Kerr microscopy, Nucleation, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Magnetization, perpendicular anisotropy, Transition metal, 0103 physical sciences, 75.60.Jk, 75.60.Ch, 75.60.Lr, 75.70.Cn, 010306 general physics, Condensed matter physics, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Condensed Matter - Other Condensed Matter, Exchange bias, exchange bias, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], 0210 nano-technology, magnetization reversal, Antiparallel (electronics), Other Condensed Matter (cond-mat.other)
Abstract

Magnetization relaxation of exchange biased (Pt/Co)5/Pt/IrMn multilayers with perpendicular anisotropy was investigated by time-resolved Kerr microscopy. Magnetization reversal occurs by nucleation and domain wall propagation for both descending and ascending applied fields, but a much larger nucleation density is observed for the descending branch, where the field is applied antiparallel to the exchange bias field direction. These results can be explained by taking into account the presence of local inhomogeneities of the exchange bias field., To appear in Physical Review B (October 2005)

Published
2005
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18. Fabrication and Characterization of Magnetic Media Deposited on Top or Side Edges of Silicon Dots

Author

Vincent Baltz, Pascale Bayle-Guillemaud, Bernard Rodmacq, Bernard Dieny, S. Landis, Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), 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)), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA ), Modélisation et Exploration des Matériaux (MEM), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
010302 applied physics, Fabrication, Materials science, Silicon, General Engineering, General Physics and Astronomy, chemistry.chemical_element, Nanotechnology, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Condensed Matter::Materials Science, chemistry, Transmission electron microscopy, Magnet, 0103 physical sciences, Patterned media, Reactive-ion etching, Magnetic force microscope, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Electron-beam lithography, ComputingMilieux_MISCELLANEOUS
Abstract

Arrays of lines and dots were patterned on silicon substrates by electron beam lithography and reactive ion etching. Co/Pt multilayers were sputter-deposited on these patterned substrates to realize perpendicular patterned media for ultra high-density magnetic recording. Magnetic material thus covers the top of the lines and dots, the bottom of the grooves between nanostructures, and to a lesser extent, the sidewalls. Magnetic properties were characterized by both macroscopic and magnetic force microscopy experiments. From the results obtained from high-resolution transmission electron microscopy (TEM) experiments, we propose a new approach for realizing patterned magnetic media using the side edges instead of the top of the dots.

Published
2004
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19. Magnetic and transport properties of single and double perpendicular magnetic tunnel junctions

Author

Cuchet, Léa, 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), Université Grenoble Alpes, Bernard Rodmacq, Ricardo Sousa, and STAR, ABES

Subjects
Spin transfer torque, Jonction tunnel magnétique, Spintronics, Couple de transfert de spin, Mram, Double barrière, [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Anisotropie magnétique perpendiculaire, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Électronique de spin, Magnetic tunnel junction, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat], Perpendicular magnetic anisotropy, Double barrier
Abstract

Due to their advantageous properties in terms of data retention, storage density and critical current density for Spin Transfer Torque (STT) switching, the magnetic tunnel junctions with perpendicular anisotropy have become predominant in the developments for MRAM applications. The aim of this thesis is to improve the anisotropy and transport properties of such structures and to realize even more complex stacks such as perpendicular double junctions. Studies on the magnetic properties and Tunnel MagnetoResistance (TMR) measurements showed that to optimize the performances of the junctions, all the thicknesses of the different layers constituting the stack have to be adapted. To guaranty both a large TMR as well a strong perpendicular anisotropy, compromises are most of the time needed. Studies as a function of magnetic thickness enabled to extract the saturation magnetization, the critical thickness and the magnetic dead layer thickness both in the bottom reference and the top storage layer in structures capped with Ta. This type of junction could be tested electrically after patterning the sample into nanopillars. Knowing that perpendicular anisotropy mostly arises at the metal/oxide interface, the Ta capping layer was replaced by a MgO one, leading to a huge increase in the anisotropy of the free layer. A second top reference was then added on such a stack to create functional perpendicular double junctions. CoFeB/insertion/CoFeB synthetic antiferromagnetic storage layers could be developed and were proved to be stable enough to replace the standard Co/Pt-based reference layers., Du fait de leurs propriétés avantageuses en termes de rétention des données, densité de stockage et faible courant critique pour l'écriture par courant polarisé en spin (STT), les jonctions tunnel magnétiques à anisotropie perpendiculaire sont devenues prédominantes dans les études sur les applications aux mémoires magnétiques MRAM. Les travaux de cette thèse s'inscrivent dans ce contexte avec pour but l'amélioration des propriétés de transport et d'anisotropie de telles structures ainsi que la réalisation d'empilements encore plus complexes tels que des doubles jonctions perpendiculaires. Grâce à l'étude des propriétés magnétiques et des mesures de MagnétoRésistance Tunnel (TMR), il apparaît que pour optimiser les performances des jonctions tunnel, l'ensemble des épaisseurs des couches composant l'empilement doit être adapté. Des compromis sont souvent nécessaires pour obtenir à la fois une forte anisotropie perpendiculaire et des signaux de TMR élevés. Des études en fonction des épaisseurs magnétiques ont permis de déterminer les aimantations à saturation, épaisseurs critiques et couches mortes dans les couches de référence et de stockage de jonctions standard avec électrode libre supérieure et couverture Ta. Ce type de jonction a pu être nano-fabriqué sous forme de piliers circulaires afin de tester l'écriture par STT. Sachant que l'anisotropie perpendiculaire provient essentiellement de l'interface métal/oxyde, la couverture Ta a été ensuite remplacée par une deuxième couche de MgO, permettant d'améliorer significativement l'anisotropie de la couche libre. En introduisant une seconde référence au-dessus de cette jonction, des doubles jonctions perpendiculaires fonctionnelles ont pu être fabriquées. Des couches de stockage antiferromagnétiques synthétiques de la forme CoFeB/insert/CoFeB ont pu être développées et apparaissent suffisamment stables pour pouvoir remplacer les traditionnelles références à base de multicouches Co/Pt.

Published
2015

20. Jonctions tunnel magnétiques à aimantation perpendiculaire : anisotropie, magnétorésistance, couplages magnétiques et renversement par couple de transfert de spin

Author

Nistor, Lavinia, 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), Université de Grenoble, Bernard Rodmacq, Alain Schuhl, and STAR, ABES

Subjects
Oxydes, [PHYS.COND.CM-GEN] Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Interlayer exchange coupling, Magnetoresistance, Couplage indirect, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Magnetic Tunnel Junctions, Perpendicular Magnetic Anisotropy, Oxides, Jonctions tunnel magnétiques, MRAM, Anisotropie magnétique perpendiculaire
Abstract

The aim of this thesis is the study of magnetic tunnel junctions with perpendicularly magnetized electrodes (pMTJ), using perpendicular magnetic anisotropy (PMA) arising from the magnetic metal/oxide interfaces. For magnetic memories applications, it was predicted in theory that perpendicular junctions should need less energy (current) for spin transfer torque (STT) writing applications. However, the engineering of such structures is a real challenge and a difficult task since simultaneous transport (TMR) and PMA properties impose constraints on materials being used and also limit the working window of the device, especially in terms of magnetic layer thickness. In order to reach our goal we first studied different properties of these structures, such as the origin of PMA from the metal/oxide interface, tunnel transport and interlayer exchange coupling phenomena. The PMA at magnetic metal/oxide interface was showed to strongly depend on different parameters like annealing temperature, oxygen concentration, layer thickness etc. Several pMTJ structures were tested in order to choose the best one for MRAM memories applications. A correlation between TMR and PMA was observed and confirms the PMA origin from the magnetic metal-oxygen bond formation at the interface. Furthermore, antiferromagnetic interlayer exchange coupling was observed in our structures in the presence of out of plane anisotropy. A detailed study was made as a function of annealing temperature and layers thickness, in order to understand the origin of this coupling and its possible relationship to the anisotropy strength. Finally the STT-pMTJ concept was validated and low critical currents were observed on submicronic dots prepared by electron beam lithography., Le but de cette thèse est l'étude des propriétés de jonctions tunnel magnétiques à aimantation perpendiculaire, en utilisant l'anisotropie perpendiculaire présente à l'interface entre un métal magnétique et un oxyde. En théorie, dans le cas des applications mémoires, les jonctions tunnel perpendiculaires devraient nécessiter moins d'énergie (courant) pour l'écriture par courant polarisé en spin. Mais la fabrication de telles structures représente un défi et une tâche difficile puisque les propriétés de transport (TMR) et d'anisotropie imposent des contraintes sur les matériaux utilisées en limitant la fenêtre de travail, notamment en ce qui concerne l'épaisseur des couches magnétiques. Pour atteindre cet objectif nous avons tout d'abord étudié les propriétés de ces structures comme l'anisotropie de l'interface métal magnétique-oxyde, le transport tunnel et le couplage entre les couches magnétiques à travers la barrière isolante. L'amplitude de l'anisotropie d'interface entre un métal magnétique et un oxyde dépend de l'épaisseur des couches magnétiques, de la température de recuit et la concentration de l'oxygène à l'interface. Différentes structures ont été réalisées afin de choisir la structure la mieux adaptée pour les applications mémoires MRAM. Une corrélation entre la TMR et l'anisotropie a été observée permettant de valider l'origine de l'anisotropie perpendiculaire : la formation de liaisons métal magnétique-oxygène. Un couplage antiferromagnétique à été aussi observé entre les couches magnétiques à anisotropie perpendiculaire à travers l'oxyde. Une étude détaillée sur le couplage a été faite en fonction de la température de recuit et de l'épaisseur des couches magnétiques pour mieux comprendre l'origine du couplage et une possible relation avec l'amplitude de l'anisotropie perpendiculaire. Finalement des jonctions perpendiculaires ont été nano-lithographiées et des mesures de commutation d'aimantation par transfert de spin sur des piliers nanométriques ont été réalisées avec de faibles courants critiques.

Published
2011

21. MAGNETORESISTANCE AND SPIN TRANSFER TORQUE IN MAGNETIC TUNNEL JUNCTIONS

Author

Manchon, Aurélien, 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), Department of Physics and Astronomy [Columbia] (Mizzou Physics), University of Missouri [Columbia] (Mizzou), University of Missouri System-University of Missouri System, Université Joseph-Fourier - Grenoble I, Bernard Rodmacq(bernard.rodmacq@cea.fr), Institut Neel (Grenoble), Synchroton ELETTRE (Trieste, IT), Universite Lomonosov (Moscou, Russie), University of Korea (Seoul, Coree), Samsung (Coree), and Manchon, Aurélien

Subjects
Spin Polarized Transport, Jonctions Tunnel Magnétiques, Magnetoresistance Tunnel, Transport Polarisé en Spin, Spin Transfer, Magnetic Anisotropy, Spin Electronics, Magnetic Tunnel Junctions, Tunnelling Magnetoresistance, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Electronique de Spin, [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat], Anisotropie Magnétique, Transfert de Spin
Abstract

The recent observation of current-induced magnetization switching (CIMS) in magnetic tunnel junctions (MTJs) has opened new possibilities of applications for spin electronics, especially with magnetic memories (MRAM). This achievement demands the accurate control of the barrier oxidation in order to obtain MTJs with good magnetic and electronic properties. Moreover, spin transfer torque is expected to show different characteristics in MTJ compared to metallic spin valves.In a first step, an experimental study of the influence of oxygen on the magnetic properties of a Pt/Co/MOx trilayers (MOx is an oxidized metal) is presented. These modifications may be used as a probe of the oxidation state of the tunnel barrier. In a second step, we study the specific properties of spin transfer torque in a MTJ. These properties are first described within a free electron model and then estimated experimentally in MgO-based MTJ through the measurement of static phase diagrams., L'observation du renversement d'aimantation induit par courant polarisé (CIMS) dans les jonctions tunnel magnétiques (JTM) a ouvert de nouvelles perspectives d'applications pour l'électronique de spin, en particulier à travers les mémoires magnétiques (MRAM). Cette réalisation exige une bonne maîtrise de l'oxydation de la barrière tunnel mais aussi une connaissance approfondie du phénomène de transfert dans ces dispositifs.En premier lieu, une étude expérimentale de l'influence de l'oxygène sur les propriétés magnétiques d'une tricouche Pt/Co/MOx (MOx est un métal oxydé) est présentée. La modification d'anisotropie magnétique due aux atomes d'oxygène peut être utilisée pour contrôler l'oxydation des barrières tunnel. Le second aspect étudié est la détermination, théorique et expérimentale, des caractéristiques du transfert de spin dans les JTM. Ces caractéristiques sont d'abord discutées à travers un modèle d'électrons libres puis estimatées expérimentalement dans des JTM à travers la réalisation de diagrammes de phase statiques.

Published
2007

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