Ibm Serves Up A Whopper Of A Magnetic Sandwich

How many digital characters can sit on a magnetic thumbtack? About 100 million, says IBM. Rivals thought Big Blue was blowing smoke last year when it predicted that so-called giant magnetoresistance (GMR) technology could produce thumbtack-size computer disk drives with 100-megabyte capacities--enough to hold more than 100 novels--by decade's end. Now, it looks as if IBM was being conservative.

Researchers at IBM's Almaden Research Center near San Jose, Calif., have just unwrapped a so-called "read/write head" that promises to stuff at least 20 times as much data onto a hard disk as today's best technology can. The current gold standard was also developed by IBM, in 1991, using ordinary magnetoresistance--similar but less potent. Since then, hard-disk capacity has been surging by 60% a year, according to market researcher Disk/Trend Inc.

Commercial versions of the experimental GMR heads, IBM says, will sense 10 billion magnetic dots per square inch. The heads' secret is an ultrathin sandwich of silver between magnetic nickel-iron "bread." Normally, the magnetic particles in the bread repel each other. But baking the sandwich and exposing it to a magnetic field causes the particles to face the same direction (BW--Apr. 18). That makes the material far more efficient at detecting magnetic spots.

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