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Hard drive technology wins the 2007 Nobel Prize for physics
Written by Daniel   
Tuesday, 09 October 2007 10:12
Hard drive technology wins the 2007 Nobel Prize for physics

By Matt Ford | Published: October 09, 2007 - 09:57AM CT
ARS Technica
Albert Fert of the Université Paris-Sud in Orsay, France and Peter Grünberg of the Forschungszentrum in Jülich, Germany have been awarded the 2007 Nobel Prize in physics for their discovery of the phenomena known as giant magnetoresistance (GMR). The two scientists independently discovered the phenomena and published their results in 1988 and 1989, respectively. This work has previously been recognized by the American Physics Society and awarded the 1994 James C. McGroddy Prize for New Materials.


Magnetoresistance is nothing new in science—it is the change in electrical resistance of a material when it is in the presence of an external magnetic field. It was measured 150 years ago by W. Thomson (Lord Kelvin), who found that the resistance of iron and nickel would change depending upon the orientation of the magnetic field relative to the material. What he discovered is now referred to as anisotropic magnetoresistance, a property of materials that arises from electron spin-orbit coupling. Normally, this is a weak phenomena, as general magnetoresistance changes the conduction in a material by only a few percent at most.

Even though this phenomena is weak, it led to the development of many important technologies, including the parts that allow us to read and write to disks. Prior to the discovery of GMR materials, the best known alloy for exploiting magnetoresistance was permalloy (Ni20Fe80), and it represented little improvement over the materials used in Lord Kelvin's time. The major breakthroughs came when the two groups started experimenting with magnetic multilayers, stacks of alternating ferromagnetic and non-magnetic metals where each layer is only a few nanometers thick. The first materials used by Furt and Grünberg's groups had stacks of iron and chromium. Testing carried out on these early magnetic mutilayers showed a decrease in resistance of up to 50 percent—far greater than any seen previously. This radical increase appeared to be an entirely new phenomena, which was named GMR....More   Comment in the Forums


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