News

Olivier d'Allivy Kelly, doctorant au laboratoire, a reçu un prix du meilleur poster au Colloque Louis Néel 2013 pour sa contribution intitulée « Dépendance en épaisseur de l’effet Hall de spin inverse dans un système ultramince YIG(7-20nm)/Pt »

Manuel Bibes, chargé de recherches au CNRS, vient de se voir décerner le EU-40 Materials Prize par l’European Materials Research Society (E-MRS)

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Skyrmions on the track
Albert Fert, Vincent Cros and João Sampaio, Nature Nanotechnology 8, 152 (2013)

Magnetic skyrmions are nanoscale spin configurations that hold promise as information carriers in ultra-dense memory and logic devices due to the extremely low spin-polarized currents needed to move them.

Deux prix de thèse au laboratoire en 2012

Antoine Dussaux est lauréat du prix Jeune Chercheur Daniel Guinier de la Société Française de Physique pour son travail de thèse intitulé "Etude des oscillations de vortex magnétiques induites par transfert de spin", sous la direction de Vincent Cros et Julie Grollier.

Self-assembled monolayers reveal their potential for molecular spintronics
Marta Galbiati, Clément Barraud, Sergio Tatay et al.,
ACS Nano (2012) & Advanced Materials (2012)

(La,Sr)MnO3 manganite (LSMO) has emerged as the standard ferromagnetic electrode in organic spintronic devices due to its high spin-polarization and air stability. Whereas organic semiconductors and polymers have been mainly envisaged to propagate spin information, self-assembled monolayers (SAMs) have been overlooked and should be considered as promising materials for molecular engineering of spintronic devices. In this way dodecyl and octadecyl phosphonic acids SAMs have been grafted over the LSMO half-metallic oxide. Alkylphosphonic acids form ordered self-assembled monolayers with the phosphonic group coordinated to the surface.

Molecular magnetic tunnel junctions using these SAMs as tunnel barriers show stable and efficient spin transport properties. Large tunnel magnetoresistance with a flat bias voltage dependence of the magnetoresistance is observed in LSMO/dodecylphosphonic acid SAM/Co nanocontacts. This opens the door to spintronic tailoring though SAM engineering and could also lead to new venues for spin injection in organic devices.

A ferroelectric memristor
A. Chanthbouala, et al., Nature Materials (2012)

Memristors are continuously tunable resistors that emulate biological synapses. Conceptualized in the 1970s, they traditionally operate by voltage-induced displacements of matter, although the details of the mechanism remain under debate. Purely electronic memristors based on well-established physical phenomena with albeit modest resistance changes have also emerged. In collaboration with scientists from the University of Cambridge and Thales Research and Technology, researchers from the Unité Mixte de Physique CNRS/Thales have just demonstrated that voltage-controlled domain configurations in ferroelectric tunnel barriers yield memristive behaviour with resistance variations exceeding two orders of magnitude and a 10 ns operation speed. Using models of ferroelectric-domain nucleation and growth, they explain the quasi-continuous resistance variations and derive a simple analytical expression for the memristive effect. The results suggest new opportunities for ferroelectrics as the hardware basis of future neuromorphic computational architectures.

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Commensurability and chaos in magnetic vortex oscillations
S. Petit-Watelot, et al., Nature Physics(2012)

Researchers at the Institute of Fundamental Electronics (CNRS / Univ. Paris-Sud) and the Unité Mixte de Physique CNRS/Thales, in collaboration with teams at City University of Hong Kong and the University of Ghent (Belgium), just highlight a phenomenon of self-modulation - and even chaotic phases - in the dynamic of magnetic vortex core, that is the central area of a few tens of nanometers in the center of the vortex. This work, which opens new perspectives on nanoscale microwave oscillators for secured communications.

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Highly efficient spin transport in epitaxial graphene on SiC
B. Dlubak et al., Nature Physics (2012)

Spin information processing is a possible new paradigm for post-CMOS electronics and efficient spin propagation over long distances is fundamental to this vision. However, despite several decades of intense research, a suitable platform is still wanting. We report here on highly efficient spin transport in two-terminal polarizer/analyser devices based on high-mobility epitaxial graphene grown on silicon carbide. Taking advantage of high-impedance injecting/detecting tunnel junctions, we show spin transport efficiencies up to 75%, spin signals in the mega-ohm range and spin diffusion lengths exceeding 100 µm. This enables spintronics in complex structures: devices and network architectures relying on spin information processing, well beyond present spintronics applications, can now be foreseen.

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Gate-controlled spin injection at the LaAlO₃/SrTiO₃ interface
N. Reyren et al, Phys. Rev. Lett. 108, 186802 (2012)

The electrical Hanle (Voight geometry) and Inverse Hanle (Faraday geometry) effect in a three-point geometry have been used to probe the electrical spin injection, at low temperature, at the direct LaAlO₃/SrTiO₃ (LAO/STO) interface from a ferromagnetic Co reservoir. The significant drop of the electrical voltage (or resistance) obtained, its very high amplification compared to the classical theory of spin injection/relaxation and the corresponding variation of the electrical spin signal upon back-gate action emphasize a preferential resonant spin injection mechanism into localized states strongly coupled to the electronic two-dimensional electron system (2-DES) in STO. A detailed analysis of our data shows that spin can be conserved from the localized states to the 2-DES by tunnelling transfer evidencing, for the first time, an efficient electrical spin injection into an oxide 2-DES.

Equal-spin Andreev reflection at high-temperature superconductor/half-metal interfaces
C. Visani et al., Nature Physics (2012)

The penetration of a superconducting current from a superconductor into a half-metallic ferromagnet is forbidden in the conventional picture of the proximity effect. However, we found resonances in the conductance spectra of superconductor/half-metal heterostructures that suggest the occurrence of unconventional equal-spin Andreev reflection, which allows for the generation and propagation of high-temperature superconducting spin currents into the half-metal. This mechanism may open the door to novel spintronic devices.

Ferroelectric manipulation of magnetic flux quanta
A. Crassous et al., Phys. Rev. Lett. 107, 247002 (2011)

Using heterostructures that combine a large-polarization ferroelectric and a high-temperature superconductor, we demonstrate the nanoscale modulation of the superconducting condensate via ferroelectric field effects. Through this mechanism, a nanoscale pattern of normal regions that mimics the ferroelectric domain structure can be created in the superconductor. This yields an energy landscape for magnetic flux quanta and, in turn, couples the local ferroelectric polarization to the local magnetic induction. We show that this form of magnetoelectric coupling, together with the possibility to reversibly design the ferroelectric domain structure, opens the door to a new class of reconfigurable superconducting nano-devices.

Spin Master Voice workshop 2011,
Château de Villiers le Mahieu, France

The AIMS of the Spin Master Voice workshop, co-organized by the Unité Mixte de Physique CNRS/Thales and the Service de Physique de l'Etat Condensé (CEA, Saclay) , are to bring together scientists and engineers interested in recent trends and developments of spin transfer mechanisms in magnetic hybrid nano-structures. The goals are to identify the experimental and theoretical opportunities of these devices as novel microwave components, the breakthroughs that are required to enhance their properties (i.e. emission power, phase noise, tunability and rf sensitivity) as well as the associated challenges in the development of advanced characterization spectroscopy.

Website: Spin Master Voice 2011

Solid-state memories based on ferroelectric tunnel junctions
A. Chanthbouala, A. Crassous et al., Nature Nanotechnology (2011)

We report non-volatile memories with OFF/ON ratios as high as 100 and write powers as low as ~ 10⁴ A/cm² at room temperature by storing data in the electric polarization direction of a ferroelectric tunnel barrier. The junctions show large, stable, reproducible and reliable tunnel electroresistance, with resistance switching occurring at the coercive voltage of ferroelectric switching. These ferroelectric devices emerge as an alternative to other resistive memories, and have the advantage of not being based on voltage-induced migration of matter at the nanoscale, but on a purely electronic mechanism.

A new approach for creating room-temperature multiferroics,
S. Valencia, A. Crassous et al., Nature Materials (2011)

Multiferroic materials possess two or more ferroic orders but have not been exploited in devices owing to the scarcity of room-temperature examples. Those that are ferromagnetic and ferroelectric have potential applications in multi-state data storage if the ferroic orders switch independently, or in electric-field controlled spintronics if the magnetoelectric coupling is strong. It is shown that, at the interface with Fe or Co, the archetypal ferroelectric BaTiO₃ simultaneously possess a magnetization and a polarization that are both spontaneous and hysteretic at room temperature. Ab initio calculations of realistic interface structures provide insight into the origin of the induced moments and bring support to this new approach for creating room-temperature multiferroics.

Vertical-current-induced domain-wall motion in MgO-based magnetic tunnel junctions with low current densities, A. Chanthbouala et al., Nature Physics (2011)

In the past few years, there have been a number of proposals for fabricating magnetic memories based on the current-induced motion of magnetic domain walls. A device that uses a novel geometry for injecting electrical currents into the sample is shown to work with current densities that are two orders of magnitude lower than in previous approaches.

Journée thématique : "Memristor : Composants et Architectures"

L'unité Mixte de Physique CNRS/Thales organise une journée thématique sur les memristor (composants et archtectures) le lundi 7 mars 2011 à l'auditorium du centre de recherche Thales Research and Technology.

Vous pouvez vous inscrire auprès de Julie Grollier; Programme de la Journée

Microélectronique : un gaz d'électrons à la surface d'un isolant ouvre la voie du transistor multi-fonctions

Des chercheurs du CNRS et de l'Université Paris-Sud 11 ont découvert comment créer une couche conductrice à la surface d'un matériau isolant et transparent très étudié pour la microélectronique du futur, le titanate de strontium (SrTiO3).

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Pierre Séneor, membre junior de l'IUF

Pierre Séneor, enseignant chercheur de l'Université Paris-Sud 11, a été nommé à l'Institut universitaire de France à titre de membre junior.

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Agnès Barthélémy, médaille d'argent 2010,

Agnès Barthélémy, professeur à l'Université Paris Sud 11 et membre senior de l'Institut Universitaire de France est lauréate de la médaille d'argent 2010 du CNRS.

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Julie Grollier, Prix Jacques Herbrand 2010

Julie Grollier, chargée de recherches CNRS au laboratoire, est la lauréate 2010 du Prix Jacques Herbrand de l'Académie des sciences.

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