News & Views item - October 2007

 

European Physicists 2007 Nobel Laureates. (October 10, 2007)

The discovery of giant magnetoresistance (GMR) secured the 2007 Nobel Prize in Physics for Albert Fert of the University of Paris-South and Peter Grünberg of Jülich Research Centre in Germany.

 

The announcement of Royal Swedish Academy of Sciences reads: "This year's physics prize is awarded for the technology that is used to read data on hard disks. It is 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.

     "In 1988 the Frenchman Albert Fert and the German Peter Grünberg each independently discovered a totally new physical effect – Giant Magnetoresistance or GMR. 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.

     "In 1997 the first read-out head based on the GMR effect was launched and this soon became the standard technology. 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."

 

As Geoff Brumfiel describes it in Nature@News: "the spins of electrons, which generate a magnetic field and can be aligned either up or down. An electron can easily pass through a material whose electrons are similarly aligned, but will encounter resistance when it passes through one with electrons aligned in the opposite direction."

 

Fert and Grünberg discovered independently that using multiple layers of magnetic and non-magnetic materials only tens of nanometres thick and the layers were organized in an alternating "up-down" alignment, all electrons passing through encountered resistance. The net effect was a rise in resistance that was much bigger than any seen before, i.e. giant magnetoresistance (GMR).

 

Michael Ross commenting on Brumfiel's article points out:

 

Dual-element magnetoresistive (MR) heads (not GMR) began replacing single-element inductive coils for the read-sensor function in commercial hard-disk drive heads in 1991. (A 1-gigabit/inch2 demonstration of an MR head was made public by IBM Reseeach in late 1988.) Making the MR element smaller -- to achieve higher data-storage densities -- began to reach practical limitations at about 5 gigbits/inch2, and multilayer GMR elements began replacing the MR sensor in late 1997. The GMR head has enabled the tremendous increases in data-storage capacities that we enjoy today -- many gigabytes (and beyond) rather than mere megabytes. The creativity and doggedness of Stuart Parkin and his many IBM colleagues turned Fert and Gruenberg's wonderful discovery from a cryogenic, high-field, slow-and-expensive-to-make (i.e. molecular beam epitaxy) lab phenomenon into the room-temperature, low-field, rapidly made (i.e. sputtering) that commercial use demands. Hail to them all for their critical roles in helping to creating today's digital wonderland!

 

And Adrian Cho writes in ScienceNOW: "Although Fert and Grünberg discovered the effect, Stuart Parkin of IBM's Almaden Research Center in San Jose, California, did much of the work to make GMR technologically useful. Stuart Wolf, a physicist at the University of Virginia, Charlottesville, says he was surprised that Parkin was not honored as well. But Tony Bland of the University of Cambridge, U.K., says that the Nobel committee apparently distinguished between the discovery and its cultivation. "This is properly a physics prize for a truly extraordinary and novel effect."

 

See also the RSAS' Information for the Public.