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October 10, 2007
Physics of Hard Drives Wins Nobel
By DENNIS OVERBYE

Two physicists who discovered how to manipulate the magnetic and electrical properties of thin layers of atoms to store vast amounts of data on tiny disks, making iPods and other wonders of modern life possible, were chosen as winners of the Nobel Prize in Physics yesterday.

Albert Fert, of the Université Paris-Sud in Orsay, France, and Peter Grünberg, of the Institute of Solid State Research at the Jülich Research Center in Germany, will share the $1.5 million prize awarded by the Royal Swedish Academy of Sciences.

They will receive the money in a ceremony in Stockholm on Dec. 10.

Dr. Fert, 69, and Dr. Grünberg, 68, each working independently in 1988, discovered an effect known as giant magnetoresistance, in which tiny changes in a magnetic field can produce huge changes in electrical resistance.

The effect is at the heart of modern gadgets that record data, music or snippets of video as a dense magnetic patchwork of zeros and ones, which is then scanned by a small head and converted to electrical signals.

“The MP3 and iPod industry would not have existed without this discovery,” Börje Johansson, a member of the Royal Swedish Academy, said, according to The Associated Press. “You would not have an iPod without this effect.”

In remarks broadcast over a speakerphone at the academy in Stockholm, Dr. Fert said: “I am so happy for my family, for my co-workers. And I am also very happy to share this with a friend.”

Experts said the discovery was one of the first triumphs of the new field of nanotechnology, the science of building and manipulating assemblies of atoms only a nanometer (a billionth of a meter) in size.

The scanning heads in today’s gizmos consist of alternating layers only a few atoms thick of a magnetic metal, like iron, and a nonmagnetic metal, like chromium. At that small size, the strange rules of quantum mechanics come into play and novel properties emerge.

The Nobel citation said Dr. Fert and Dr. Grünberg’s work also heralded the advent of a new, even smaller and denser type of memory storage called spintronics, in which information is stored and processed by manipulating the spins of electrons.

Engineers have been recording information magnetically and reading it out electrically since the dawn of the computer age, but as they have endeavored to pack more and more data onto their machines, they have been forced to use smaller and fainter magnetic inscriptions and thus more and more sensitive readout devices.

It has long been known that magnetic fields can affect the electrical resistance of magnetic materials like iron. Current flows more easily along field lines than across them. The effect was useful for sensing magnetic fields, and in heads that read magnetic disks. But it amounted to only a small change in resistance, and physicists did not think there were many prospects for improvement.

So it was a surprise in 1988 when groups led by Dr. Fert at the Laboratoire de Physique des Solides and by Dr. Grünberg found that super-slim sandwiches of iron and chromium showed enhanced sensitivity to magnetic fields — “giant magnetoresistance,” as Dr. Fert called it. The name stuck.

The reason for the effect has to do with what physicists call the spin of electrons. When the magnetic layers of the sandwich have their fields pointing in the same direction, electrons whose spin points along that direction can migrate freely through the sandwich, but electrons that point in another direction get scattered.

If, however, one of the magnetic layers is perturbed, by, say, reading a small signal, it can flip its direction so that its field runs opposite to the other one. In that case, no matter which way an electron points, it will be scattered and hindered from moving through the layers, greatly increasing the electrical resistance of the sandwich.

As Phillip Schewe, of the American Institute of Physics, explained, “You’ve leveraged a weak bit of magnetism into a robust bit of electricity.”

Subsequently, Stuart Parkin, now of I.B.M., came up with an easier way to produce the sandwiches on an industrial scale. The first commercial devices using giant magnetoresistance effect were produced in 1997.

Dr. Grünberg was born in Pilsen in what is now the Czech Republic and obtained his Ph.D. from the Darmstadt University of Technology in Germany in 1969. He has been asked many times over the years when he was going to win the big prize, and so was not surprised to win the Nobel, according to The A.P.

He said he was looking forward to being able to pursue his research without applying for grants for “every tiny bit.”

Dr. Fert was born in Carcassonne, France, and received his Ph.D. at the Université Paris-Sud in 1970. He told The A.P. that it was impossible to predict where modern physics is going to go.

“These days when I go to my grocer and see him type on a computer, I say, ‘Wow, he’s using something I put together in my mind,’” Dr. Fert said.

Copyright 2007 The New York Times Company
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