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Magnetic tips sees fine detail, lost data.

If you need more memory in your computer, or if you think computer programs that retrieve lost data files and "fix" bad disks work miracles, then you'll really like this new application of scanning tunneling microscopy (STM).

Scientists typically use STM to get atomic-scale images of the surfaces of materials. These researchers use a very fine metal tip to scan a surface. Variations in the current created as electrons hop the varying distances between the tip and the surface enable them to map the material's topography.

Two years ago, John Moreland and Paul Rice of the National Institute of Standards and Technology (NIST) in Boulder, Colo., reported that they could measure variations in magnetic force across a surface by replacing the standard metal STM tip with a flexible, magnetic one. The new tip allows scientists to see these variations more easily and in much finer detail than they would with other imaging techniques, says physicist Romel D. Gomez. In the Feb. 16 APPLIED PHYSICS LETTERS, Gomez and his colleagues at the University of Maryland in College Park detail the theoretical underpinnings of magnetic-force STM and say they have improved the resolution by tilting the tip as it scans.

"The theory tells you that the image you get is directly the field that you see on the surface," Gomez says. The tip moves closer to or farther from the surface depending on the strength and direction of the surface's magnetic field at any given point. That distance alters the current between the tip and the surface, so the hills and valleys in the resulting image show in submicron detail how the magnetic field changes.

"It's a much more sensitive way of reading magnetic domains, which will allow us to have very high-density computers," Gomez adds.

A computer stores information on hard disks by creating microscopic patterns of magnetization on the disk. When it erases or writes over data, the computer covers the old magnetization pattern with a new one. Under the magnetic STM tip, this pattern shows up with greater resolution than a computer can read, says Gomez. In addition, the magnetic tip can "read between the lines," detecting old patterns of magnetization -- erased data -- as well.

NIST has a patent pending for using this technique to image and alter magnetization patterns on surfaces.
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Title Annotation:computer storage
Author:Pennisi, Elizabeth
Publication:Science News
Date:Feb 29, 1992
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