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Collaboration between researchers from the University of Chicago(1)
, from the Los Alamos National Laboratory(2) , and from
the Centre de recherche sur la matière divisée(3)
(Center for Research into Divided Matter , CRMD, a joint CNRS and Université
d’Orléans research unit) has made it possible to find paramagnetic
materials that are capable of measuring, with very high precision (about
1/1000), magnetic fields of as high as 60 teslas(4) ,
i.e. over one million times the Earth's magnetic field. These materials
are compounds based on silver and on selenium or tellurium, Ag2Se and
Ag2Te. This work has been published in Nature in its issue of May
23, 2002.
Measuring magnetic field is essential for numerous applications, ranging
from medical imaging using nuclear magnetic resonance(5)
to magnetic devices for recording and reading information. Hence the importance
of finding materials capable of measuring magnetic fields under conditions
that are as varied as possible for very wide ranges of magnetic fields
and of temperatures.
Silver, selenium, and tellurium are not magnetic materials, but the electrical
resistance of compounds based on them can be made very sensitive to magnetic
fields by adding a small quantity of silver (about 1/10,000). Their resistance
increases linearly with increasing magnetic field without showing saturation,
which makes these compounds very advantageous as magnetic field sensors.
They can also be used in technologies based on very short magnetic pulse
experiments. For example, with synchrotron radiation from third or fourth
generation sources, it would be possible to measure a diffraction pattern
with a single X-ray pulse of duration shorter than 100 picoseconds (10-12
seconds) which, subsequently, could reach 100 femtoseconds (10-15
seconds).
The Centre de recherche sur la matière divisée, directed
by Marie-Louise Saboungi, is devoted to studying all divided forms of
matter (suspensions, gels, pastes porous solids, fibers, composites, thin
layers, or aggregates). It studies how this division state controls the
way in which the material is organized, is deformed, and how it reacts
thermally, chemically, and electrochemically, etc. Synthesizing and shaping
new divided or ultra-divided materials (nano-materials), understanding
how they function, and improving their properties for storing or converting
energy, for storing or separating gases, catalysis, civil engineering,
and aeronautical engineering are its main lines of research. This program
is focused on three themes: complex systems and disordered porous media,
functional divided materials, nano-organized interface systems.
(1)
Anke Husmann and Prof. Thomas Rosenbaum
(2) Jon Betts, Greg Boebinger and Albert Migliori
(3) Matter is not always homogeneous. Substances as common
as mud, clay, cement, glass, soap, and coal, as precious as opal, or as
complex as a biological tissue are all representatives of divided matter.
What characterizes it is that it is made up of an assembly of elementary
structural units that are mesoscopic, i.e. small compared with our macroscopic
scale, but large compared with the atomic scale. These units pile up,
combine, become entangled, or disperse. The term "microtexture"
is used to describe the way they are mutually organized in space, often
hierarchically, nearly always disordered and intrinsically heterogeneous.
For more information: http://crmd.cnrs-orleans.fr/
(4) 1 tesla = 10,000 gauss
(5) Nuclear magnetic resonance (NMR) imaging has become
a medical diagnosis tool, and it is based on measuring the magnetization
that appears in tissues when a subject is placed in a magnetic field.
Researcher
contact:
Marie-Louise Saboungi
Director of the Centre de recherche sur la matière divisée
Tel: +33 2 38 25 53 77 or 79
e-mail: saboungi@cnrs-orleans.fr
Press contact :
Magali Sarazin
Tel : +33 1 44 96 46 06
e-mail : magali.sarazin@cnrs-dir.fr
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