From computers to credit cards to cloud servers, today’s technology relies on magnets to hold encoded data in place on a storage device. But a magnet’s size limits storage capacity; even a paper-thin magnet takes up space that could be better used for encoding information.
Now, for a study published in Nature Communications, researchers have engineered a magnet among the world’s thinnest—a flexible sheet of zinc oxide and cobalt just one atom thick. “That means we can store larger amounts of data using the same amount of materials,” says University of California, Berkeley, engineer Jie Yao, the study’s senior author.
Beyond slimming down conventional data storage, magnets less than one nanometer thick are indispensable for developing spintronics (short for spin electronics): gadgets that use an electron’s spin direction, rather than its charge, to encode data. Such magnets could even help excite electrons into a “quantum superposition,” which lets particles occupy multiple states simultaneously. That way, data could potentially be stored using three states—spinning up or down, or both ways at once—instead of the usual two.
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Ordinarily, nanoscale magnets must be supercooled to temperatures as low as –320 degrees Fahrenheit to maintain magnetic fields. This requirement presents a big obstacle to creating commercial spintronic devices or shrinking conventional data storage. “You don’t want to carry a cryogenic cooler with you,” says University of Chicago spintronics researcher David Awschalom, who was not involved in the study. “So having a material that’s compact and flexible at room temperature is quite important.”
The new magnet’s two-dimensional lattice functions perfectly at room temperature—and it even stays magnetized in conditions hot enough to boil water. The decision to combine these particular elements was critical; zinc and oxygen by themselves are not magnetic, but they interact with magnetic metals such as cobalt. By adjusting the ratio of cobalt atoms to zinc oxide molecules, the team “tuned” the materials’ magnetic intensity. Around 12 percent cobalt was their sweet spot—at less than 6 percent the magnet was too weak to be effective, and at more than 15 percent it became unstable.
Yao thinks wandering electrons from the zinc oxide help to stabilize the cobalt atoms, keeping the magnetic field intact. “The current hypothesis,” Yao says, “is that the electrons serve as a messenger that allows these cobalt atoms to ‘talk’ to each other.”
Computational physicist Stefano Sanvito of Trinity College in Ireland, who was also not involved in the study, says the magnet’s usefulness will depend on how it interacts with other 2-D materials. Stacking layers of various single-atom films “like a deck of cards,” he says, will let engineers tailor the next generation of spintronics for a host of applications, from secure data encryption to quantum computing: “It’s going to be very fun.”