Crowding memory into magnetic territory.

Crowding memory into magnetic territory

Igine cramming the information of a 20-volume encyclopedia into a single volume. A team of scientists and engineers at IBM's Almaden Research Center in San Jose, Calif., has achieved a comparable feat in magnetic data storage technology. By crowding 1 billion data bits -- or 1 gigabit, equivalent to almost 1,000 issues of SCIENCE NEWS -- onto a single square inch of disk surface, they claim to have made the world's most densely packed magnetic storage device.

Barry H. Schechtman, Almaden's manager of storage systems and technology, says this represents a 10- to 20-fold increase over the storage capacity of even next-generation magnetic hard disks. Commercial applications are several years away, he adds.

Increasing storage capacity requires either storing bits on tinier lots of a disk's real estate or improving the detection resolution of the head that reads the bits written on the disk. The IBM researchers pursued both tacks. A combination of precise fabrication methods and a specially composed magnetic cobalt alloy enabled them to store 158,000 bits in each inch-long segment of the 6,350 memory lanes in a radial inch. That amounts to 1,003,300,000 bits per square inch -- too dense for reliable reading by conventional inductive heads, which detect data when magnetically stored bits passing underneath induce tiny electrical currents in them. Using methods common in the semiconductor industry, the IBM researchers microfabricated novel heads capable of nearly error-free reading of ultrasmall bits at rates that rank with those of today's fastest systems, they say. The heart of the head is a magneto-resistive nickel-iron alloy that responds swiftly to each bit's magnetic field by changing its electrical resistance.