Resistance at low magnetic fields.

Certain materials change their electrical resistance when placed in a magnetic field. Known as magnetoresistance, this effect can be detected in such metals as iron. in 1988, researchers discovered that they could enhance this minor effect considerably by using the right type of layered material, and since then scientists have vied to formulate new materials that show larger and larger resistance changes for a given magnetic field (SN: 8/29/92, p.140).

Now, Todd L. Hylton and his colleagues at IBM ADSTAR in San Jose, Calif., report in the Aug. 20 SC(ENCE the discovery of a new method of producing "giant magnetoresistance" at much lower magnetic fields than previously possible-comparable to those required for storing data on magnetic disks. They achieve the effect by creating alternating layers of silver and nickel-iron, then quickly heating and cooling the structure to allow some silver atoms to diffuse into the nickel-iron. Such materials may eventually allow the storage of 30 times more data on a computer disk than now possible.