A New Spin on Mobile Memory
By Mark Frauenfelder, Thu Jul 22 21:00:00 GMT 2004

The makers of tiny hard drives would like to see their products installed in the next generation of mobile devices, but a nanostorage technology called spintronics that's starting to creep out of R&D labs might mean spinning disks aren't the best choice for mobile storage.


When I got my first job out of engineering school in 1984, I went to work for Memorex, in Santa Clara, California. We were developing a 100-megabyte hard disk. The platters were 14 inches in diameter and the drive weighed about 70 pounds. If you dropped one, you could kiss your data, and possibly a toe, goodbye. Times sure have changed. Toshiba now has a postage-stamp sized hard drive with a 0.85-inch platter. Measuring 3.3 x 24 x 32mm, the drive weighs 10 grams and has a capacity of 2 gigabytes.

But even this miniature marvel (the world's smallest to date) isn't small enough for the mobile phone industry. It's a bit too thick for mobiles, which have been designed to accommodate a 2.1mm SD card slot. (A Chinese company, GS Magicstor, has announced it will be making a 0.8 inch diameter disk drive, but hasn't released any other specs yet.) And, as with all hard drives, there are also power, reliability and cost concerns associated with hard drives.

For the time being, solid state memory must serve the needs of phones as they continue to become more powerful, offering music, video and other storage-hungry capabilities. Unlike batteries, solid-state memory does follow Moore's law. As a result, the storage capacity of mobile phones has shot up over the years, as expected. But the fun won't last forever. In as little as five years, flash memory will bump up against physical fabrication limits, and refuse to ascend any higher up Moore's curve.

But by that time, it's likely that spintronics will step in to carry the torch. Spintronics is a field of nanotechnology that uses the directional spin of electrons to indicate the "1s" and "0s" of binary computation. Nanotechnology is the science of making microscopic structures that exploit the unusual properties of materials at the nanometer level. (For reference, a nanometer is approximately 1/100,000th the thickness of a human hair.) MRAM, short for Magneto Resistive Random Access Memory, is the furthest along of several nascent spintronics nanotechnologies. MRAM is likely to play a major role in portable memory in the upcoming years, because it combines many of the benefits (and very few of the disadvantages) of hard drives, flash memory, SRAM and DRAM.

To find out more, I spoke to nanotechnology expert Howard Lovy, the principal author of a new report on nanostorage that was issued this week by the market research firm, NanoMarkets.

Lovy told me the one big advantage of MRAM is instant access. Compared to hard drives and flash memory, which are relatively slow, MRAM is speedy. It's not as fast as SRAM, but unlike SRAM, MRAM is nonvolatile, which means the data doesn't go "poof!" when the power is cut off. MRAM could give mobile phones a much-desired instant-on (and off!) capability.

MRAM also uses a lot less power than solid-state memory since it doesn't have to be continuously refreshed. It only uses power when it is being accessed, and even then, it only needs a small amount. Another advantage is the ultra-high storage capacities that are achievable. "It brings us into the terabyte territory," says Lovy. Were talking not just your entire music library on a chip, but the entire Library of Congress on a sugar cube."

MRAM isn't at that level yet, but Freescale (formerly Motorola's semiconductor unit), the leading player in the field of at least eight companies working on MRAM, says it'll be ready to sell 4Mbit nanostorage chips by the end of this year. "We have customers evaluating MRAM for mobile communications, office products, security and controls systems, networking and storage products," says Kris Murray, a company spokesperson.

Four Mbits is relatively puny -- but so is the chip, which at 10.29 x 18.54 x 1.20mm is less than a tenth the size of Toshiba's tiny hard drive -- however, it represents a huge leap over the 1Mbit MRAM chip Freescale made in 2002. In fact, MRAM densities have been ramping up faster than Moore's law. The most recent MRAM jump is "like stepping over four or five process generations in little more than a year," said Bob Merritt, vice president of emerging technologies with Semico Research Corp. There's no guarantee, of course, that MRAM densities will continue to shoot up at that rate, but even if they settle down, one thing's for certain -- spinning electrons are going to give spinning disks a run for their money.