BOFFINS AT IBM claim to have developed a technique to store and retrieve data from a single atom. In comparison, current magnetic hard-disk drives require around 100,000 atoms to store a single 'bit', while current best-effort research has achieved storage on between three and 12 atoms.
The researchers used Holmium (Ho) atoms on a bed of magnesium oxide. Holmium is a rare earth element and part of the lanthanide series of metallic chemical elements. Holmium on magnesium oxide has a property called ‘magnetic bistability', which is to say it can have two stable magnetic states.
"To demonstrate independent reading and writing, we built an atomic-scale structure with two Holmium bits, to which we write the four possible states and which we read out both magneto-resistively and remotely by electron spin resonance," claim the researchers in their paper.
"The high magnetic stability combined with electrical reading and writing shows that single-atom magnetic memory is indeed possible."
The researchers applied a magnetic state to the atoms using a scanning tunnelling microscope to apply 150 millivolts at 10 micro-amps to one atom. This causes the atom to switch its magnetic state. The magnetic state of the atom can be detected because each state has a different level of conductivity. Applying a lower voltage and sensing its resistance reveals its magnetic state.
The researchers independently tested its magnetic state by parking an iron atom next to it. The way in which the iron atom responds - because it is naturally magnetic - corroborated the changed magnetic state of the holmium atom.
They added, however, that the magnetic state lasted, at least, a number of hours, and that its longer-term stability is not yet known. However, the researchers admit that the state of the atoms could become unstable as they are heated. A practical use of the technique, therefore, would require a number of the atoms coupled together.
The techniques are explained in technical detail in the latest issue of the journal Nature. µ
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