NEW ORLEANS, La.— ­The tiniest electronic gadgets have nothing on this new device to store data. It encodes each bit of data using the magnetic field of a single atom. This makes for extremely compact data storage. The rub: So far, researchers have stored only two bits of data this way.

A bit is the smallest unit of data, equal to a zero or one. “If you can make your bit smaller, you can store more information,” says Fabian Natterer. He’s a physicist at the École Polytechnique Fédérale de Lausanne in Switzerland. Natterer described his team’s achievement March 16 at a meeting, here, of the American Physical Society. His group also shared their results in the March 9 Nature.

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The researchers created the super-tiny magnetic bits using atoms of the metal holmium. They placed the atoms onto a surface of magnesium oxide. The direction of each atom’s magnetic field served as a zero or one. Which it was depended on whether its north pole was pointing up or down.

Using a special microscope, the scientists could flip an atom’s magnetic orientation. This would switch a bit from 0 to 1 — or back again. To read out the data, the researchers measured the electric current running through the atom. That current will depend on the orientation of the magnetic field.

To ensure that such a change in current was due to a flipping of the atom’s magnetic field, the team added bystander atoms of iron. (This allowed the scientists to check how the holmium atoms’ magnetic fields had affected the iron atoms.)

The new system could lead to new hard drives that store data much more densely than has been possible. Today’s data systems need 10,000 atoms or more to store a single bit of information.

Natterer also hopes to use these mini magnets to construct materials with fine-tuned magnetic properties. They could be built up one atom at a time. “You can play with them,” he explains. He likened them to Lego blocks.