A tiny magnetic sensor made at the University at Buffalo could lead to a big advance in computer memory storage, researchers said. The sensor, made of nickel and only a few atoms wide, is many times more sensitive to changes in magnetic resistance than existing "read heads" for computer disk drives.
That's important because the smaller and more sensitive the read head, the more data can be stored on the disk.
Magnetic disks store data on PCs and also on computer "servers" that ladle up pages on the World Wide Web.
"The magnitude of the (magnetic) effect is larger than anybody else has found," said William Egelhoff Jr., a research chemist at the National Institute of Standards and Technology in Gaithersburg, Md. "It's very promising."
Engineering teachers Harsh Deep Chopra and Susan Hua, a husband- and-wife research team at UB, published their findings in the July 1 issue of Physical Review B.
If the sensor proves technologically feasible, the advance could become part of commercial disk drives within five or 10 years, Egelhoff said. Between now and then lie many hurdles, such as being able to manufacture the item, that could eliminate the sensor for commercial use.
Changes in resistance on a magnetic disk are interpreted as "bits" of zeros and ones, the basic units of computer data.
"If you want to increase data storage capacity, you make the zeros and ones smaller," Chopra said. But "as you reduce the size, the field gets weaker and weaker, so it's harder to detect."
Chopra and Hua used "nanoscale" fabrication techniques to fashion an ultra-sharp tip on a wire of nickle. When passed over a magnetized area of a disk, it sensed a change in electrical resistance of 3,000 percent -- compared to changes of less than 100 percent in today's read heads.
The research was funded by the National Science Foundation and U.S. Department of Energy.
The tiny size of the sensor contributes to its high sensitivity. Because it is only a few atoms wide and long, the sensor displays an effect called "ballistic magnetoresistance," in which free electrons zoom through a conductor in a straight line. Larger read heads measure a different effect called "giant magnetoresistance," where the zig-zag paths taken by electrons dilute sensitivity.
"The breakthrough came in recognizing how to shape a sliver of atoms," Chopra said. Teachers of mechanical and aerospace engineering, the pair devised an electrical deposition process to attach a tip, just a few billionths of a meter in size, to the end of a nickel wire.
If adapted to disk drives, the technology could boost storage capacity to 1 trillion bits on a surface the size of a credit card, or enough to hold about 50 DVDs -- 49 more than current technology.
Other research teams around the world are also working on higher- capacity data storage, according to industry experts. The UB technique has an advantage in that it would work on current- technology magnetized disks. Other storage techniques, such as physical marks temporarily melted into the surface of the disk, would require a massive change-over of manufacturing equipment.
Now the UB team is working on making the fabrication technique repeatable, enhancing its commercial value.