Thursday, January 12, 2012

Physics & Math

Smallest magnetic memory uses just 12 atoms

Talk about doing more with less. A dozen atoms have been made to store a bit of data magnetically – a feat normally performed by a million atoms. The work could one day help shrink the devices that store computer data.
Today's hard drives record data using a tiny electromagnet to align the spins of atoms in a metallic film that rotates below it. When the spins of about a million of these atoms are aligned in the same direction, their collective magnetic field can be detected by the electromagnet on its next pass. This means the million-strong group stores a single bit of data – a 1 or a 0 in binary code.
Unfortunately, that collective magnetic field also affects adjacent bits, limiting how closely they can be packed. Now Andreas Heinrich of IBM Research Almaden in San Jose, California, and colleagues have made the smallest magnetic bits yet – and they can be packed more closely together than today's much larger bits.
The trick is to make adjacent atoms spin in opposite directions. This alignment, called antiferromagnetism, does not generate an external magnetic field.

Densely packed

Using a scanning tunneling microscope, the researchers were able to encode a bit of data in just 12 iron atoms kept at a temperature just a few degrees above absolute zero. Smaller numbers of atoms were too unstable to act as bits – without neighbours to interact with and stabilise them, the atoms behaved like quantum objects that existed in multiple spin states at once.

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