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2Physics Quote:
"Stars with a mass of more than about 8 times the solar mass usually end in a supernova explosion. Before and during this explosion new elements, stable and radioactive, are formed by nuclear reactions and a large fraction of their mass is ejected with high velocities into the surrounding space. Most of the new elements are in the mass range until Fe, because there the nuclear binding energies are the largest. If such an explosion happens close to the sun it can be expected that part of the debris might enter the solar system and therefore should leave a signature on the planets and their moons." -- Thomas Faestermann, Gunther Korschinek (Read Full Article: "Recent Supernova Debris on the Moon" )

Tuesday, October 09, 2007

Physics Nobel Prize 2007 for 'Giant Magnetoresistance'

Albert Fert (left) and Peter Grünberg (right) [Photo Courtesy: Unité mixte de physique CNRS/Thales, Orsay and Institut für Festkörperforschung, Forschungszentrum Jülich ]

Laptops, iPods and so many other small-sized devices that have defined a new generation of our civilization owe a large part of their existence to the discovery of a fundamental effect in Physics about 19 years back and this year's Nobel Prize celebrates this path-breaking advancement that influenced so much the growth of the computer industry and days of our lives.

The Royal Swedish Academy of Sciences has awarded the Nobel Prize in physics for 2007 jointly to Albert Fert (France) and Peter Grünberg (Germany) for the discovery of 'Giant Magnetoresistance’ or GMR.

Albert Fert is currently professor at Université Paris-Sud, Orsay, since 1976 and scientific director of the Unité mixte de physique CNRS/Thales, Orsay, since 1995. He earned his PhD in 1970 at the Université Paris-Sud. He was born on 7 March 1938 at Carcassonne. Peter Grünberg is a Professor at Institut für Festkörperforschung, Forschungszentrum Jülich, Germany, since 1972. He was born on May 18, 1939. Grünberg received his Ph.D in 1969 at Darmstadt University of Technology in Germany.

About 'Giant Magnetoresistance’ (GMR): In 1988 the Frenchman Albert Fert and the German Peter Grünberg each independently discovered this totally new physical effect. They observed that very weak magnetic changes give rise to major differences in electrical resistance in a GMR system. A system of this kind is the perfect tool for reading data from hard disks when information registered magnetically has to be converted to electric current.

A hard disk stores information, such as music, in the form of microscopically small areas magnetized in different directions. The information is retrieved by a read-out head that scans the disk and registers the magnetic changes. The smaller and more compact the hard disk, the smaller and weaker the individual magnetic areas. More sensitive read-out heads are therefore required if information has to be packed more densely on a hard disk. A read-out head based on the GMR effect can convert very small magnetic changes into differences in electrical resistance and therefore into changes in the current emitted by the read-out head. The current is the signal from the read-out head and its different strengths represent ones and zeros.

Soon after the discovery of Fert and Grünberg, researchers and engineers began work to enable use of the effect in read-out heads. In 1997 the first read-out head based on the GMR effect was launched and this soon became the standard technology. Thanks to this technology that it has been possible to miniaturize hard disks so radically in recent years. Sensitive read-out heads are needed to be able to read data from the compact hard disks used in laptops and some music players, for instance. Even the most recent read-out techniques of today are further developments of GMR.

"The GMR effect was discovered thanks to new techniques developed during the 1970s to produce very thin layers of different materials. If GMR is to work, structures consisting of layers that are only a few atoms thick have to be produced. For this reason GMR can also be considered one of the first real applications of the promising field of nanotechnology", The Royal Swedish Academy of Sciences said.

Homepage of Albert Fert: http://www2.cnrs.fr/en/338.htm
Homepage of Peter Grünberg: http://www.fz-juelich.de/portal/gruenberg/

Those Historic Papers:
"Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices",
M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Eitenne, G. Creuzet, A. Friederich, J. Chazelas,

Phys. Rev. Lett. 61, 2472, (1988), Abstract.
"Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange",
G. Binasch, P. Grünberg, F. Saurenbach, and W. Zinn,
Phys. Rev. B 39 (7), 4828-4830 (1989). Abstract.

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At 6:49 AM, Anonymous Peter McClelland said...

Great posting! I liked that you cared to put links to those two historic papers. Your presentation is always superb.


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