Not Flipping Out

From September 29th, 2007; Vol.172 #13 (p. 205)

Scientists have shown for the first time how single atoms may be able to magnetically encode single bits of information.

Hard disks store data by magnetizing small domains of a disk’s surface so that the magnetic axis points in one of two opposing directions. Each orientation is stable because the domain’s energy is at a minimum. Such stability helps keep the magnetic axis from wandering, which would corrupt the data.

To fit more data onto a surface, engineers would like to shrink the domains, working toward the ultimate limit of single atoms. But reliable data storage would still require energy-minimizing orientations to prevent random flips.

Cyrus Hirjibehedin of IBM’s Almaden Research Center, in San Jose, Calif., and his colleagues used a scanning tunneling microscope to place iron or manganese atoms on a copper-nitrogen surface and to sense the atoms’ spins—the atomic version of their magnetic axes. The interaction of the atoms with the surface’s structure gave rise to preferred, energy-minimizing directions, the team reports in the Aug. 31 Science.

The surface was kept at just 0.5 kelvin, but Hirjibehedin says that the team’s method may eventually lead to configurations of one atom or more that will produce a stable magnetic orientation at higher temperatures.

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