Researchers at the IBM Almaden Labs south of San Jose, CA have experimentally set the lower bound on magnetic storage at 12 atoms. It appears that eight atoms can’t quite cut it. Although the atoms are iron atoms, their antiferromagnetic properties provide the storage mechanism, not the ferromagnetic properties. Because the ferromagnetic properties tend to link adjacent atoms, the antiferromagnetic arrangement used in this latest experiment apparently alternates the magnetic spin directions of adjacent atoms, creating a more stable arrangement. Here’s the byte worth of magnetic storage the IBM researchers assembled using a Scanning Tunneling Microscope, shown in five different states that represent the five ASCII characters in the IBM watchword “THINK”:
It appears that each bit in the byte consists of two rows of six atoms apiece, arranged with alternating magnetic spins. Adjacent atoms in the same row have stable alternating spins while adjacent atoms across rows within the bit have the same spin.
Normally, for a ferromagnetic storage cell in one of today’s hard drives, you’d try to get all of the spins oriented the same way for maximum signal.The antiferromagnetic approach seems to code the bit in the spin sequence rather than trying to orient all the spins in the same way.
For comparison, the densest hard drives currently employ roughly one million atoms to represent a bit. Antiferromagnetic storage promises to improve that density by five orders of magnitude.
Here’s a cool video of the development:
Don’t jump up from your chair just yet and rush out to Fry’s or Best Buy for one of these superdense antiferromagnetic hard drives, however. You won’t be buying hard drives based on this technology soon. Most of the world isn’t ready for cryo-cooled hard drives and you need a 5 Kelvin (–451°F) refrigerator to make this technique work.
See the IBM press release here. http://www-03.ibm.com/press/us/en/pressrelease/36473.wss