October 9, 2007

2007 Physics Nobel Awarded for Hard Drive Technology

College Park – Albert Fert (Université Paris-Sud, Orsay, France) and Peter Grünberg (Forschungszentrum Jülich, Germany) have won the 2007 Nobel Prize in physics for the discovery of giant magnetoresistance (GMR), the phenomenon at the heart of read-heads in high density hard drives and other devices that require highly sensitive detection of magnetic fields.

GMR is the dramatic variation in the electrical resistance of multilayered thin film structures that occurs with application of a magnetic field. The applied field changes the relative orientations of magnetic regions in some of the layers. When the fields in adjacent layers are aligned, electrons with spins oriented parallel to the fields (up electrons) pass easily from one layer to another, and antiparallel (down) electrons are strongly scattered, leading to low resistivity for up electrons. If adjacent regions have fields pointing in opposite directions, both spin up and spin down electrons are strongly scattered, and the resistance is high for all electrons. It is the spin-based explanation for GMR that has led to the use of the term "spin valve" for various GMR devices.

Magnetic sensors and the read-heads in high density computer storage media are among the common devices to benefit from GMR, and nonvolatile, low-power, high-density magnetic random access memory (MRAM) may soon replace dynamic random access memory (DRAM) in personal computers. Arguably, the most promising GMR-derived applications are still in their infancy; spin-selective active devices, such as transistors, are only now being perfected, but they have already inspired a new term in the scientific nomenclature: spintronics. Potentially, spin-selective components may even offer a practical avenue to optical and quantum computers.

While the Nobel Laureates made their discoveries independently, both published their fundamental work in papers submitted to the Physical Review journals in 1988. The work of Fert and colleagues first appeared in Physical Review Letters (PRL) November 21, 1988, and is one of the top ten most frequently cited PRL papers in the journal’s history. Grünberg and colleagues’ paper in Physical Review B was published March 1, 1989, although they had submitted their work to the journal nine months earlier.

“Few discoveries in physics have equaled GMR in so rapidly revolutionizing the technologies that we rely on in our daily lives,” says APS Editor-in-Chief Gene Sprouse. “We’re proud that the fundamental work of Fert and Grünberg first appeared in journals of the American Physical Society.”

In fact, the APS anticipated this year’s Nobel with the 1994 McGroddy Prize for New Materials, which recognized Fert and Grünberg, along with Stuart Parkin of IBM, for their GMR discoveries.

"The work of Fert and Grünberg generated great excitement in the condensed matter physics community when it first appeared in the APS journals almost twenty years ago,” says Joe Serene, APS Treasurer and Publisher, “but none of us realized how important giant magnetoresistance would become in our daily lives. It’s already revolutionized data storage in personal computers, and may soon revolutionize the processors themselves. This is a marvelous example of the way that whole new technologies, like the GMR-based field of spintronics, can grow out of fundamental research in basic physics of the sort that we publish in the journals of the American Physical Society, and of the need for our nation to continue to invest in basic research."

Relevant Links:

APS News: PRL Top Ten number 6, Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices
www.aps.org/publications/apsnews/200303/prl-6.cfm

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. Creuset, A. Friederich, and J. Chazelas, Phys. Rev. Lett. 61 (1988) 2472
link.aps.org/abstract/PRL/v61/p2472

Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange, G. Binasch, P. Grünberg, F. Saurenbach, and W. Zinn, Phys. Rev. B 39 (1989) 4828
link.aps.org/abstract/PRB/v39/p4828