Faits marquants 2015

2D nanoporous graphene : a route to organic topological insulators ?

The electronic and structural properties of a system are tightly connected and by experimenting with structure researchers are able to play with quantum electronic properties. Ultimately-thin materials like graphene (a single plane of carbon atoms) provide numerous illustrations of properties dominated by low-dimensionality. Full text

Strong roundceramic superconducting wires for very high field magnets

High magnetic fields have many advanced applications. In medical Magnetic Resonance Imaging they make it possible to scan the soft tissues of the human body, in Nuclear Magnetic Resonance spectroscopy, they enable studies of molecular structure and molecular interactions. Magnetic fields curve the paths of charged particles in circular particle accelerators like the Large Hadron Collider at CERN. Full text

Chiral domain walls in thin magnetic films

Magnetic domain walls are the transition regions between two magnetic domains with different magnetization directions. In ultra-thin films of a magnetic metal such as cobalt, having magnetization perpendicular to the film plane, the domain walls can be very narrow : 5 - 20 nm. Full text

The PHYSIQUARIUM, a visitors’ area at the Institut NÉEL

This dedicated visitors’ area aims to make the story of scientific advances- past and presentcomprehensible and attractive, and to provide glimpses of future developments. It was planned as a gateway to the Institut NÉEL’s research work, adaptable for a varied public. It provides a pedagogical presentation of our work, including possibilities for simple demonstration experiments. Full text

Implementing X-Ray diffraction/scattering tomography in the lab

Real materials often exhibit a complex and heterogeneous organization. Their distinctive functionalities are linked to their specific structure at the atomic scale as observed in alloys, cements but also in teeth, bones or archaeological materials. Full text

Longdistance entanglement between spins in quantum spin chains

The macroscopic world surrounding us is much more complex than it was thought by the greatest scientists of the 19th century and before. After the mathematical completion of the most significant theory of the 20th century, quantum mechanics, it became clear that new concepts had to be incorporated, although they may defy common sense and human perception may have difficulty accepting such strange predictions. This is the concept called “entanglement”. Full text

Creation and manipulation of magnetic monopoles in spin ice

Condensed matter near the absolute zero of temperature reveals much exotic physics associated with unusual orders and excitations, with examples ranging from helium superfluidity to magnetic monopoles in the solid materials called “spin ices”. Full text

Synchrotron X-Ray study of platinumnanoparticle catalysts

Better knowledge of metal nanoclusters supported on an oxide is of paramount fundamental and technological importance especially in the field of energy. In particular, dispersed platinum particles on alumina (aluminium oxide Al2O3) are widely used as heterogeneous catalysts, from the laboratory scale to the industrial plant. Full text

Multifunctional substrate holder for a film- deposition system

Many of the Institut NÉEL’s research projects require constructing specialist equipment inlaboratory, to precise specifications. We describe here a technical development that has greatly improved a system used for high-rate deposition of thick magnetic films onto silicon substrates by DC sputtering. These films are studied for their functional magnetic properties and their integration into novel microsystems. Full text

Imaging inside Gallium Nitride wires for next generation blue LEDs

Semiconductors are both fascinating for physicists and extremely useful to society. The best-known semiconductor is Silicon, the material at the origin of the electronics and digital revolution of the second half of the 20th century. Full text

TeraHertz properties of multiferroic compounds

Electromagnetic waves outside the spectrum of visible light have been used for over a century to carry information (radio waves) or probe matter (X-Rays). Full text

Resistivity, magnetism and shape memory in martensitic alloys

The martensitic phase transformation plays an important role in transformations of the microstructure and plasticity of many materials. The term martensite referred originally to a structural phase of carbon steel alloys named after German metallurgist A. Martens. Full text

Imaging interfaces in artificial semiconductor crystals

Many electronic and optoelectronic devices are fabricated from semiconducting “superlattices” : a sequence of alternating, thin layers of two different semiconducting compounds that have the same crystal structure. A superlattice is like a single crystal, but one that has periodic, abrupt changes of composition at the interfaces between its two constituent compounds. Full text

Measuring the phase shift of an electron scattered by a single spin

Quantum interference is one of the most mysterious features of quantum mechanics. A well-known example is the Young double-slit experiment which demonstrates that light can be described at the same time by a particle picture and by a wave picture – the famous particle-wave duality. Full text

Probing light fields with nano-mechanical oscillators

Because of their ultra-low mass, nanometre-scale objects can be used to measure applied forces with exceptional sensitivity, provided one can detect their vibrations. Full text

Metal colloids investigated by enhanced- Raman correlation spectroscopy

Metal colloids are suspensions of nanometre-size gold or silver particles dispersed in a liquid, here water. Under illumination by light, these solutions present unique and amazing optical properties that depend strongly on the size, shape and state of aggregation of the particles. Full text

Coherent control of a single nuclear spin with an electric field

Over the last four decades, the size of a bit, the smallest logical unit in a computer, has decreased by more than two orders of magnitude and will soon reach a limit where quantum phenomena become important. Inspired by the power of quantum mechanics, researchers have already identified pure quantum systems that have controllable and readable discrete states, in analogy with a classical bit. Full text

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