'Instant-On' Memory Device May Give Hard Drive the Boot

A radical new magnetic memory device that could eliminate the need for hard drives and provide "instant-on" capabilities for a wide range of consumer products has moved closer to the production line.

One major advantage of the new technology is the memory system is nonvolatile, meaning it does not lose its contents when the power is turned off. Thus there is no need for a hard drive to "refresh" the cells in the memory device, eliminating the need to reboot a computer every time it is turned on.

The technology is purely electronic, thus eliminating the mechanical features that can lead to failures with hard drives. And the potential for memory storage is enormous.

"We anticipate we can put 400 gigabits in a square inch," said solid state physicist Gary Prinz of the Naval Research Laboratory, which has just contracted with a pioneering Minnesota firm to move the technology from the lab to the production line.

A number of industrial giants, including Honeywell, Motorola and IBM, are working on various applications for the technology, but the Naval Research Laboratory claims to have taken it a step further than anyone else.

The Navy, of course, is not particularly concerned about how much time we waste while our personal computers fire up, or how little memory we have in our digital cameras, but it is very interested in memory systems that can be turned on instantly.

"We don't like hard drives," said Larry Cooper, program manager at the Office of Naval Research, which is funding the project. "There's a lot of applications where we want instant-on computing."

It's a bit uncomfortable to wait even a few seconds for a battlefield computer to fire up and identify a target, for example.

The new technology doesn't even use transistors as on-off switches that record the digital data of zeros and ones, and that could bring the cost down, researchers said. Instead of transistors, the technology uses unthinkably small magnetic "doughnuts" whose ability to transmit an electric current is influenced by the presence of a magnetic field.

If a doughnut's resistance is strong enough, the magnet is "on," and if not, it is "off." Thus millions of tiny doughnut-shaped magnets on a chip could record the digital information and remember it even after the power is turned off.

What's neat about the technology is that the smaller they can make it, the better it works, Prinz said, making it particularly useful for portable devices.

The Navy has contracted with the small Minnesota firm of Nonvolatile Electronics Inc. to develop the technology to produce the devices on a commercial scale. The company was founded in 1989 by James Daughton, who pioneered the field with Honeywell, and it has already carved out a sizable market for magnetic sensors and other devices based on similar technology.

Prinz has briefed a number of manufacturing companies to see whether they thought there would be any problem in large-scale manufacturing. "They assured us that's not a problem," Prinz said.

The field has been a hot issue since 1988 when researchers in France and Germany were working with thin layers of metallic and nonmetallic films, Prinz said. The researchers discovered that the presence of a magnetic field changes the electrical resistance of a thin metal film by as much as 6%.

That was considered a large effect, so they gave it a name: vertical giant magnetoresistance random access memory, or VRAM. It has since picked up a few other names, including MRAM, for magnetic random access memory.

The effect may have been large, but not large enough to have been of much use.

"A lot of people have been trying to figure out what to do with this" ever since the discovery, Prinz said.

The research took a significant turn when Michigan State University got into the act, he said. Other researchers had applied the current parallel to the layers, but Michigan scientists sent the current down through the layers "like driving a nail down through a phone book," Prinz said.

"They found a fivefold increase in the effect, and that really caught my attention," he said. It opened the possibility of creating tiny magnets on the sub-micron scale needed for memory storage systems.

With the help of Jian-Gang Zhu, professor of electrical and computer engineering at Carnegie Mellon University, Prinz set out to build a memory storage device using the Michigan technique. He soon discovered that the magnetic resistance--which would turn the magnets on or off--was too weak if the device was too large.

"Imagine a wire," Prinz explained. "A very fat wire has very low resistance, but a very skinny wire has high resistance. So my task was to make little stacks of metallic layers, like poker chips, but to make the diameter of those poker chips extremely small."

He ended up with tiny poker chips with a hole in the middle to confine the magnetic field, so they are more like doughnuts than poker chips. They measured 0.6 micron in diameter--so small they could be seen only with an electron microscope, and Prinz hopes to cut that size in half next year.

The doughnuts were packed onto the surface of a chip with a network of wires below and above the devices to selectively turn them on and off.

"They only have two states, so you get digital information," he said. "You have either a one or a zero out of each of these elements."

Unlike a semiconductor chip, which loses its information when the power is turned off, the magnetic device retains the data like a hard disk. No rebooting is necessary.

The device is so small, and requires so little power, that it should be possible to combine it with a computer's central processing unit, according to Max Yoder, director of electronics operations at the Office of Naval Research.

That would eliminate the long wires needed to connect the memory to the control unit, "so the whole computer operation itself will be significantly speeded up," Yoder said.

Researchers believe the technology could lead to storage chips with up to 1,000 times the capacity of current devices. They could be especially useful in small, hand-held instruments with large memory requirements, such as digital cameras, and where it is impractical to rely on a hard disk, such as the battlefield.

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Lee Dye can be reached at leedye@gci.net.

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