Unexpectedly long-range effects in advanced magnet...( A tiny grid pattern has led material...)

A tiny grid pattern has led materials scientists at the National Institute of Standards and Technology (NIST) and the Institute of Solid State Physics in Russia to an unexpected findingthe surprisingly strong and long-range effects of certain electromagnetic nanostructures used in data storage. Their recently reported findings* may add new scientific challenges to the design and manufacture of future ultra-high density data storage devices.

The team was studying the behavior of nanoscale structures that sandwich thin layers of materials with differing magnetic properties. In the past few decades such structures have been the subjects of intense research because they can have unusual and valuable magnetic properties. The data read heads on modern high-density disk drives usually exploit a version of the giant magnetoresistance (GMR) effect, which uses such layered structures for extremely sensitive magnetic field detectors. Arrays of nanoscale sandwiches of a similar type might be used in future data storage devices that would outdo even today's astonishingly capacious microdrives because in principle the structures could be made even smaller than the minimum practical size for the magnetic islands that record data on hard disk drives, according to NIST metallurgist Robert Shull.

The key trick is to cover a thin layer of a ferromagnetic material, in which the magnetic direction of electrons, or "spins," tend to order themselves in the same direction, with an antiferromagnetic layer in which the spins tend to orient in opposite directions. By itself, the ferromagnetic layer will tend to magnetize in the direction of an externally imposed magnetic fieldand just as easily magnetize in the opposite direction if the external field is reversed. For reasons that are still debated, the presence of the antiferromagnetic layer changes this. It biases the ferromagnet in one preferred direction, essentially pinning its field in that orientation. In a mag
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