It seems that our appetite for data is growing faster than ever, doubling every year. So researchers are always trying to find new solutions. This time, scientists from the National Institute of Standards and Technology (NIST) and the University of Arizona, Tucson, have made nanodot arrays that respond to magnetic fields with record levels of uniformity and that could be key for future nanodot-based drives with at least 100 times the capacity of today's hard disk drives.
Here are the explanations given by the NIST.
A nanodot has north and south poles like a tiny bar magnet and switches back and forth (or between 0 and 1) in response to a strong magnetic field. Generally, the smaller the dot, the stronger the field required to induce the switch. Until now researchers have been unable to understand and control a wide variation in nanodot switching response. The NIST team significantly reduced the variation to less than 5 percent of the average switching field and also identified what is believed to be the key cause of variability -- the design of the multilayer films that serve as the starting material for the nanodots.
Nanodots, as small as 50 nanometers (nm) wide, were fabricated using electron beam lithography to pattern multilayer thin films. The key was to first lay down a tantalum "seed layer" just a few nanometers thick when making a multilayer film of alternating layers of cobalt and palladium on a silicon wafer. The seed layer can alter the strain, orientation or texture of the film. By making and comparing different types of multilayer stacks, the researchers were able to isolate the effects of different seed layers on switching behavior. They also were able to eliminate factors previously suspected to be critical, such as lithographic variations, nanodot shape or crystal grain boundaries.
Below is a "false-color image of 50-nanometer cobalt-palladium nanodots made with a magnetic force microscope provides both topographic and magnetic profiles. The darker dots are magnetized in the up direction (representing 1 in binary code) and the lighter dots are pointing down (representing 0)." (Credit for image and caption: Justin M. Shaw, NIST)
The five researchers involved are Justin Shaw, William Rippard, and Stephen Russek, from NIST, and Timothy Reith and Charles Falco, of the Thin Films group at the University of Arizona, Tucson. Their research work has been recently published by the Journal of Applied Physics under the name "Origins of switching field distributions in perpendicular magnetic nanodot arrays" (Volume 101, Issue 2, Article 023909, January 15, 2007). Here is a link to the abstract.
Finally, don't forget that years should pass before this technology leads to commercially viable hard drives.
Sources: National Institute of Standards and Technology (NIST), via EurekAlert!, January 19, 2007; and various other websites
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