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IBM Researchers Create New "Self-assembling" Magnetic Materials

Could Lead to 100-Fold Increase in Computer Data-Storage Density

SAN JOSE, Calif. & YORKTOWN HEIGHTS, N.Y - 17 Mar 2000: -- IBM researchers have combined nanotechnology with chemistry to make a radically new class of magnetic materials that may one day allow computer hard disks and other data-storage systems to store more than 100 times more data than today's products.

A team of scientists from IBM Research's laboratories in New York and California have discovered chemical reactions that cause tiny magnetic particles, each uniformly containing only a few thousand atoms, to self-assemble -- or automatically arrange themselves -- into well-ordered arrays with each particle separated from its neighbors by the same preset distance.

Only 4 nanometers (billionths of a meter) in diameter, some 20,000 of these tiny "nanoparticles" containing a mixture of iron and platinum would be needed to span a human hair. The new reactions also permit precise control of both the size of the "nanoparticles" and their separation distance, factors that are important in increasing data density.

"This scientific discovery could lead to new solutions for storing the huge volumes of data generated worldwide as our customers incorporate the Internet and e-business into their livelihoods," said Currie Munce, IBM Research's Director of Storage Systems and Technology. "Many practical considerations must still be addressed before this new process will be suitable for manufacturing disks, but it's an exciting and promising laboratory development.

"This achievement also demonstrates the breadth of our technical leadership in our industry, which is aimed at providing the most capable products to our customers," Munce said. Coincidentally, IBM on Wednesday (March 15) announced two new record-breaking disk drive products -- the highest capacity disk drive (Deskstar 75GXP -- 75 Gigabytes) and the drive with the highest data density (Deskstar 40GV -- 14.3 gigabits per square inch).

"With self-assembly, we let Nature do most of the work," said Dr. Shouheng Sun, the lead scientist of the IBM Research team. "This new process opens up new options for thinking about how we might make future high-density data storage media."

The IBM scientists who created the new material process are: Drs. Sun and Christopher Murray of IBM's Thomas J. Watson Research Center in Yorktown Heights, New York; and Drs. Dieter Weller, Liesl Folks and Andreas Moser of the Almaden Research Center in San Jose, Calif. They described their work in Friday's issue (March 17, 2000) of Science Magazine.

Technical details

To make the magnetic nanoparticles, the IBM scientists combine two specially selected iron- and platinum-containing molecules (iron carbonyl and platinum acetylacetonate) in a heated solution. As the molecules react with each other, the iron and platinum separate from their organic segments and coalesce into spherical nanoparticles of an iron-platinum alloy each containing several thousand atoms in about equal elemental proportions. Surrounding the growing nanoparticles is a flexible layer of surfactant molecules (oleic acid and oleyl amine) that, like spokes extending in all directions from the center of a ball, keep the particles physically and magnetically independent as they self-assemble into a regular array as the solvent is allowed to evaporate. Further heating in the absence of oxygen bakes the surfactant coating around each particle into a hard carbon shell that locks the particles into place and prevents corrosion of the film when it is subsequently exposed to air. This heating (also called "annealing") also causes a critical change in the atomic structure within each particle: The iron and platinum atoms rearrange themselves from a useless form that does not retain its magnetic orientation (face-centered cubic) to a very useful one that does (face-centered tetragonal).

The 4 nm-diameter nanoparticles are not only about half the average size of the individual magnetic grains of the sputtered magnetic media IBM used to record its record-setting density of 35.3 billion bits per square inch in October 1999, but they are also some 10 times more uniform in size. Smaller magnetic particles can enable smaller data bits, and in general, a more uniform particle size also usually permits smaller data bits to be detected more easily and accurately with existing signal detection and error-correction schemes. Combining both desirable qualities in the same material can lead to even greater data density gains.

But as with any radically new discovery, there are many unknowns and important practical considerations that need to be studied and overcome before this new nanoparticulate material could be considered for use as a practical media for disk-drive recording. Known issues include: the durability, smoothness and chemical stability of the material; the means for controlling magnetic orientations, long-range packing uniformity and consistency over an entire 3.5-inch disk surface; manufacturing costs and throughputs; compatibility with the other materials and processes used to make disks, and the relative gains in noise performance compared with media made by extending existing sputtered-film media.

Even if these technical hurdles are overcome, the benefits of the new material would have to outweigh the costs of installing new equipment and making changes in the existing manufacturing process. Today, precise combinations of magnetic and alloying elements are sputtered directly onto the disk substrate within a vacuum chamber. The new nanoparticulate method may require returning to the spin-on-film method of disk-coating that sputtering replaced a decade ago, while retaining the extremely high precision required of today's disk media.

The farther future

Looking farther into the future, since each of these nanoparticles is already magnetically stable at room temperature, this new process may facilitate the ultimate in data-storage density: storing one data bit in a single tiny grain of magnetic material rather than the several hundred to 1,000 grains used today.

"But achieving such a lofty goal entails even more daunting challenges." says Dr. Weller. "Scientifically, we must understand the science of single-particle magnetization, while on the engineering side, we must be able to align the read/write head precisely over each particle as it passes rapidly on the spinning disk."

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Images of the new material and diagrams showing the novel process are available.

Contact(s) information

Mike Ross
IBM's Almaden Research Center
(408) 927-1283

Charles Jenkins
IBM's T.J. Watson Research Center
(914) 945-3499

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