Storage device of just 12 atoms
The findings, being reported Thursday in the journal Science, could help lead to a new class of nanomaterials for a generation of memory chips and disk drives that will not only have greater capabilities than the current silicon-based computers but will also consume significantly less power. And it may offer a new direction for research in quantum computing.
"Magnetic materials are extremely useful and strategically important to many major economies, but there aren't that many of them," said Shan X Wang, director of the Center for Magnetic Nanotechnology at Stanford University. "To make a brand new material is very intriguing and scientifically very important."
Until now, the most advanced magnetic storage systems have needed about 1 million atoms to store a digital 1 or 0. The new achievement is the product of a heated international race between two elite physics laboratories to explore the properties of magnetic materials at a far smaller scale.
Last May, a group at the Institute of Applied Physics at the University of Hamburg in Germany reported on the ability to perform computer logic operations on an atomic level.
The group at IBM's Almaden Research Center here, led by Andreas Heinrich, has now created the smallest possible unit of magnetic storage by painstakingly arranging two rows of six iron atoms on a surface of copper nitrite atoms. The cluster of atoms is described as anti-ferromagnetic - a rare quality in which each atom in the array has an opposed magnetic orientation. (In common ferromagnetic materials like iron, nickel and cobalt, the atoms are magnetically aligned.)
Under the laboratory's founder, Don Eigler, IBM has explored the science of nanomaterials far smaller than the silicon chips used in today's semiconductors. Eigler recently retired from the company but is a co-author of the Science paper.
The researchers now use a scanning tunneling microscope, which looks like a giant washing machine festooned with aluminum foil, not only to capture images of atoms but to reposition individual atoms - much the way a billiard ball might be moved by a pool cue with a sticky tip.
Although the research took place at temperatures near absolute zero, the scientists wrote that the same experiment could be done at room temperature with as few as 150 atoms.
As part of its demonstration of the anti-ferromagnetic storage effect, the researchers created a computer byte, or character, out of an individually placed array of 96 atoms. They then used the array to encode the IBM motto "Think" by repeatedly programming the memory block to store representations of its five letters.
Moreover, Heinrich said, smaller groups of atoms begin to exhibit quantum mechanical behavior - simultaneously existing in both "spin" states, in effect 1 and 0 at the same time. In theory, such atoms could be assembled into Qbits - the basic unit of an experimental approach to computing that might one day push beyond the capabilities of today's most powerful supercomputers.
"If you do this with two atoms, then they behave more like a quantum mechanical object," Heinrich said. "This is why science is interested in this work more than the technology."
In an interview in a small laboratory office here, he said he was planning to knock out a wall to create room for an expanded effort in exploring the quantum mechanical properties of the anti-ferromagnetic effect.
"This is really where we live," he said. "If you step outside of the press release, we are trying to control the quantum mechanics of this spin behavior to coax them to do whatever we want them to do."
Computer industry analysts said the IBM effort heralded a new direction for nanotechnology and that it might offer a route to new kinds of nanomaterials.
"Nanotechnology labs are going to begin asking, 'What else is going on down there?"' said Richard Doherty of Envisioneering, an industry consulting firm based in Seaford, NY. "The information storage side of this is fantastic, but this truly changes our ideas of the behavior of materials at molecular levels."
Currently, anti-ferromagnetic materials are instrumental in two different types of data storage products. They are essential for the manufacture of the phonograph-needle-like recording heads used in today's hard-disk drives. They are also used in a new type of memory chip known as spin-transfer-torque RAM, or STT-RAM, which is viewed by some as a future competitor for both DRAM and Flash memory chips.
Heinrich said that the tiny devices built with scanning tunneling microscopes would never be more than laboratory experiments. However, he noted that many research groups are exploring different ways of designing novel materials using self-assembly methods ranging from mechanical to biological approaches.
Industry executives said that as the semiconductor industry draws closer to exhausting the ability to scale down today's circuits using lithographic tools that etch patterns on the surface of silicon wafers, an intense international hunt is under way for a manufacturing technology beyond microelectronics.
"The nation that discovers the next logic switch will lead the nano electronics era and reap the economic rewards associated with it," said Ian Steff, vice president for global policy and technology partnerships for the Semiconductor Industry Association.
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