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Micrograph of one of IBM’s pioneering giant magnetoresistive (GMR) heads, the most sensitive of its kind for writing and reading data on a computer’s magnetic hard disk drive. By passing a pattern of current pulses through the large coil in the center of the image, magnetic fields are induced and concentrated at a tiny gap, located beneath the tip in the lower center. The fields, in turn, write bits onto the hard disk as a concentric pattern of magnetized regions called a data track. To read the bits, the magnetic fields emanating from the disk change the electrical conductivity of an extremely sensitive GMR element, which sits right behind the gap. Electronics in the disk drive detect the conductivity changes and convert them back into a pattern of digital data.
In 1997, IBM was first to introduce the GMR head into products, stimulating hard-disk-drive data densities to increase from 60 percent to 100 percent (doubling) each year.
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