To makers of computer disk drives, the fainter the magnetic field a sensor can detect, the better. If data-reading heads can detect tinier data bits, which have weaker fields, manufacturers can cram more data into less disk space (SN: 4/3/99, p. 223).
Today, commercial read heads are made of layers of magnetic metals stacked into sandwich structures whose electrical resistance changes in response to a varying magnetic field. These so-called giant magnetoresistance heads change their resistance at room temperature by about 5 percent in the presence of a magnetic bit of data, says Stuart A. Solin of NEC Research Institute in Princeton, N.J.
In the Sept. 1 Science, he and his colleagues unveil a new type of magnetoresistive device about the size of a pinhead. More like a traffic rotary for electrons than a sandwich, it could raise commercially useful magnetoresistance to new heights.