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Headlines 2009

17-11-2009

Making still smaller and less power consuming digital memories for mobile electronics? Scientists from CNRS and University Paris Sud XI (Laboratory of Solid State Physics, CNRS / Univ. Paris-Sud 11 and Institut Néel) and CEA-IRAMIS come to demonstrate the feasibility, thanks to a new class, said multiferroic, of materials combining unusual electrical and magnetic properties.


This text is a translation of the joint press release from CEA-CNRS-Univ. Paris XI

In a study published in Physical Review Letters, scientists from the Laboratory of Solid State Physics (CNRS / Université Paris-Sud XI), the "Institut Rayonnement-matière Saclay (CEA IRAMIS)"  and the "Institut Néel" (CNRS) validate the concept of data writing and storage via an electric field, an advantageous technological way for miniaturization memories.

At the microscopic level, atoms and molecules produce electrical and magnetic fields. At our level, in most crystals, the electrical and magnetic properties of the atoms are balanced and cancel each other. Sometimes this is not the case, and for some compounds, known as ferromagnetic, the magnetic properties remain at the macroscopic scale: they may well serve as a magnet. More rarely, for compounds called ferroelectric, an electric order remains at the macroscopic scale. More rarely, both electric and magnetic exist together: this is the case of multiferroic materials. Moreover, in these materials, electrical and magnetic orders interact. Such interaction provides an opportunity to control the spins (magnetic moments of atoms) via an electric field, which represents a considerable challenge especially for information storage.

16-11-2009
O.Bezencenet, A.Barbier, D.Bonamy, R.Belkhou (SOLEIL), P.Ohresser (SOLEIL)

With the advent of spin electronics (spintronics), it became particularly important to visualize and understand how magnetic domains form in magnetic structures. This is particularly tricky for antiferromagnetic layers, which show no macroscopic magnetization and therefore interact weakly with probes.

Antiferromagnetic layers are essential elements in magnetic heterostructures where they are used to pin the magnetization of adjacent layers via magnetic exchange coupling. This type of structure is the basis of operation of modern magnetic sensors (giant magnetoresistance sensors, spin valves and tunnel junctions) and will most likely be incorporated into non-volatile magnetic memories of the future as well as in genuine multiferroic structures. The magnetic domain walls determine the level of noise in electronic devices. It is therefore particularly important and challenging to master them.

30-09-2009
F. Mallet, F. Ong, A. Palacios, F. Nguyen, P. Bertet, Denis Vion and D. Esteve

After the realization in 2002 of one of the first solid state quantum bits (qubits), scientists from the Quantronique IRAMIS-SPEC research group have performed a further step towards the realization of  an elementary quantum processor: the accurate and non destructive readout of such a qubit.

07-09-2009
D. Dulić, P. Lavie, S. Campidelli, A. Filoramo, collaboration : F. Pump et G. Cuniberti (Université de Dresde)

 

 

Scientists at the Laboratory of Molecular Electronics (IRAMIS / SPEC) recently published a paper entitled  "Controlled Stability of Molecular Junctions" in the prestigious international journal Angewandte Chemie. The work done in collaboration with the group of Prof. Gianaurelio Cuniberti of the University of Dresden shows the influence of the contact interfaces on transport through single molecules by means of the break-junction method.

04-12-2009

Scientists at the "Laboratoire de chimie et biologie des métaux" (CEA-CNRS-Université J. Fourier, CEA-Grenoble), "Laboratoire de chimie des surfaces et interfaces" (CEA-Saclay) and a team at the Laboratoire d'innovation pour les technologies des énergies nouvelles et les nanomatériaux" (CEA Grenoble) have combined nanoscience and bio-inspired chemistry to develop, for the 1st time, a paltinum free material capable of catalyzing both production of hydrogen and its use in a fuel cell.

This result, important in view of a more competitive hydrogen economy is being published in the journal Science.

22-09-2009
D. Kopetzki, Y. Michina, T. Gustavsson, D. Carrière

Amphiphilic molecules have a hydrophilic head and a hydrophobic chain. Under certain conditions, they can self-organize into hollow spherical hollow vesicles with a surfactant bilayer enclosing an aqueous core, the overall diameter ranging from a few tens of nanometers to several microns. By carefully choosing specific preparation conditions, the scientists of SIS2M have shown that extremely robust aggregates can be synthesized with an interesting potential for encapsulation.

The vesicles are widely studied for many fundamental issues (mechanism of self-assembly, physical properties of the membrane, etc ...) which understanding may open new perspectives (controlled release of active molecules, chemical nanoreactors, energy conversion, etc...). Usually, these vesicles (in this case also known as "liposomes") are prepared from phospholipids, that also form cell membranes. It would be advantageous to replace the phospholipids with molecules with similar properties but with more accessible or easily modified chemical functions, such as fatty acids molecules. It was already possible to synthesize such vesicles of fatty acids in specific conditions of temperature and pH, but the way to stabilize them was yet to be found: they are indeed very sensitive to external conditions and are destroyed easily to give micelles or crystals.

04-12-2009

Scientists at the "Laboratoire de chimie et biologie des métaux" (CEA-CNRS-Université J. Fourier, CEA-Grenoble), "Laboratoire de chimie des surfaces et interfaces" (CEA-Saclay) and a team at the Laboratoire d'innovation pour les technologies des énergies nouvelles et les nanomatériaux" (CEA Grenoble) have combined nanoscience and bio-inspired chemistry to develop, for the 1st time, a paltinum free material capable of catalyzing both production of hydrogen and its use in a fuel cell.

This result, important in view of a more competitive hydrogen economy is being published in the journal Science.

06-07-2009
Contact CEA : Hamed Merdji

In photography, the scattered light from an illuminated object is recorded with a detector and one get an image of it. If the image is formed with an objective, the optics imposes many limitations (resolution, aberrations ...). To achieve the ultimate resolution, spatially (function of the wavelength of the radiation used) and temporally (function of the "flash" duration), one possible technique (without any optics) is the coherent diffraction. Using a coherent beam like a laser to illuminate the object, a signal modulation due to interference is present and allows digitally reconstructing the exact image of the object with an unprecedented precision. To achieve nanometer or even atomic resolution, we therefore enlighten with a beam of coherent X-rays (radiation laser wavelength nanometer) and record the image. The usually low average illumination requires long accumulations over several laser shots. Recent advances have yielded images with a single shot femtosecond (10-15 s) from a laser laboratory, opening the way for time resolved studies.

For regular arrangements of elementary objects, the Bragg diffraction of X-rays is a powerful technique for characterization of matter at the atomic scale. It is the primary tool for crystallography. The information contained in the Bragg diffraction is rich: if a is the characteristic size of the elementary object, the Bragg peaks are spaced by 1/a in reciprocal space. However, some information is lost: indeed, the maximum frequency at which the diffraction pattern can be sampled is less than the Nyquist frequency (2a). In particular, if the elementary object has an amplitude and a phase, the phase is lost in the Bragg diffraction.

 

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