(credit: S. Rittner and R. Hulet, Rice University)
Magnetic media, in the form of tapes and disks, have had a long run as the primary means of digital storage. In this hardware, clusters of magnetic atoms are set in a single magnetic orientation, which can be read back to determine whether a bit has a value of one or zero. Advances in capacity mostly come from figuring out how to make those clusters smaller. The ultimate limit, of course, would be a single atom, but here, quantum fluctuations will keep the bit from being stored stably. Single atom magnets have been created, but they have ended up holding a random value within a fraction of a second.
Now, a team of Swiss researchers has identified the two quantum effects that cause most of the problems for these single atom magnets and figured out how to limit them. The result is a device where individual atoms can hold onto their orientation for dozens of minutes. The big downside? It needs to be kept near absolute zero to work.
Magnetism in a bulk material, like a bar magnet, arises from the behavior of individual atoms within the material—more specifically, the behavior of some of the electrons orbiting those atoms. Although it would be possible for individual atoms to flip their orientation, the magnetic field created by all the neighboring atoms makes doing so very improbable. As a result, groups of atoms tend to maintain their orientation indefinitely, allowing us to stably write bits to them.
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