The smallest magnetic-memory bit ever made—an aggregation of just 12 iron atoms created by researchers at IBM—shows the ultimate limits of future data-storage systems.
The magnetic memory elements don’t work in the same way that today’s hard drives work, and, in theory, they can be much smaller without becoming unstable. Data-storage arrays made from these atomic bits would be about 100 times denser than anything that can be built today. But the 12 atoms making up each bit must be painstakingly assembled using an expensive and complex microscope, and the bits can hold data for only a few hours and at low temperatures approaching absolute zero, so the miniscule memory elements won’t be found in consumer devices anytime soon.
As the semiconductor industry bumps up against the limits of scaling by making memory and computation devices ever smaller, the IBM Almaden research group, led by Andreas Heinrich, is working from the other end, building computing elements atom-by-atom in the lab.
The necessary technology for large-scale manufacturing at the single-atom scale doesn’t exist yet. Today, says Heinrich, the question is, “What is it you would want to build on the scale of atoms for data storage and computation, in the distant future?”
As engineers miniaturize conventional devices, they’re finding that quantum physics, which never had to be accounted for in the past, makes devices less stable. As conventional magnetic memory bits are miniaturized, for example, each bit’s magnetic field begins to affect its neighbors’, weakening each bit’s ability to hold on to a 1 or a 0.
The IBM researchers found that it was possible to sidestep this problem by using groups of atoms that display a different kind of magnetism. The key, says Heinrich, is the magnetic spin of each individual atom.
In conventional magnets, whether they’re found holding up a note on the refrigerator or in a data-storage array, the magnetic spins of the atoms are aligned. It’s this alignment that leads to instability when magnetic-memory elements are miniaturized. The IBM researchers made their tiny memory elements by lining up iron atoms whose spins were counter-aligned.